摘要:

1 Introduction By F. J. BERRY Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK and N. G. CONNELLY School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK In Volume 94 of Annual Reports, Section A we continue to achieve our aim of covering progress in inorganic chemistry both by Group and by subjects of special interest; this year the special topics are supplemented by a chapter on Mechanisms and Kinetics in the Solid State.All areas of interest to inorganic chemists continue to flourish. Agreement has at last been reached on the names of elements 101–109, in some cases after many years of controversy; proposals for elements 110–112 are about to be considered. The possibility of triple bonding between gallium and transition metals has attracted considerable attention; the first reported Nb–– – Nb triple bond, the first Ti––Te bond, and the shortest iron–iron bond yet structurally determined are less contentious but as remarkable.As well as unusual structural features, other ‘firsts’ continue to be reported, including a molecular TmII complex, primary phosphido complexes of lanthanides, and a remarkable bis(pentalene) compound of thorium.Though not the most abundant of elements, exploration of the chemistry of seaborgium shows it to be similar to Mo and W. Noble metal chemistry provides excellent examples of new potential applications, including a zeolite-encapsulated photoactive RuII complex as a photochemical battery, a homogeneous dehydrogenation catalyst that does not require a sacrifical hydride acceptor, silver chalcogenides with giant magnetoresistance and photochemical energy storage by crystals of an unusual ‘stacked’ gold trimer.Synthetic and structural studies, together with the enormous current interest in reaction mechanisms and bioinorganic chemistry (now routinely making very e§ective use of site-directed mutagenesis) illustrate the vigour and vibrancy of this area of inorganic chemistry.In main group chemistry we have seen the development of novel chiral molecules in which a Group 15 element plays the role of a donor atom. Especially vibrant areas are those in which the molecules contain both nitrogen and phosphorus within a chiral aromatic or ferrocenyl framework. Within Group 16, tellurium continues to exhibit the most impressive array of novel structural types, for example [Te 8 ]2` (isostructural with the long known ions [S 8 ]2` and [Se 8 ]2`) and [Cr 4 (CO) 20 Te 4 ], the organometallic derivative of a Te allotrope.That is not to say that interesting species have not emerged from work with the other Group 16 elements. One fascinating result comes in the form of [NH 4 ] 3 [Ir(S 4 )(S 6 ) 2 ], originally formulated as [NH 4 ] 3 [IrS 15 ] as long as Royal Society of Chemistry–Annual Reports–Book A 11904.The fact that the formulation was so close is testimony to the excellence of the original work. Intriguingly, the fact that the material in question resolves spontaneously upon crystallisation means that enantiomeric crystals were available to the original workers a decade before Werner first separated optically active inorganic complexes.The highlight for 1997 in Noble Gas chemistry must be the confirmation of a Xe–Xe bond. Nineteen years after the reported existence of the dark green Xe 2 ` cation, a structural characterisation of the [Sb 4 F 21 ]~ salt has demonstrated the presence of a Xe–Xe bond which is longer than any other main group element–element bond.Considerable strides have been made in the control of the regio- and stereochemistry of polyaddition of [60]-, [70]- and even [78]-fullerenes, leading to the synthesis of fullerene derivatives with previously unobtainable addition patterns. There has also been a considerable e§ort into the controlled production of carbon nanotube-based materials which has resulted, for example, in the bulk preparation of single-walled carbon nanotubes, bundles of aligned nanotubes, and samples consisting entirely of graphite conical structures.The impressive electromechanical amplifier based on a single [60]fullerene molecule clearly demonstrates the potential of fullerene-based materials in future nanotechnology applications.As far as new solids are concerned, 1997 saw the continued development and sophistication of hydrothermal methods of synthesis, including reports of interesting new alumino- and zinco-phosphates with very low framework densities, and the second report of a 14-membered ring zeolite having circular 10Å diameter channels. More exotic non-oxide systems such as tellurides and nitrides are also beginning to be systematically explored.We also note the work on vanadate anodes with high lithium capacities implying an alternative intercalation mechanism. The high performance of solid oxide fuel cells using a thin film of yttrium-stabilised zirconia and another using doped lanthanum gallates is also noteworthy. 2 F. J. Berry and N. G. Connelly 1 Introduction By F.J. BERRY Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK and N. G. CONNELLY School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK In Volume 94 of Annual Reports, Section A we continue to achieve our aim of covering progress in inorganic chemistry both by Group and by subjects of special interest; this year the special topics are supplemented by a chapter on Mechanisms and Kinetics in the Solid State.All areas of interest to inorganic chemists continue to flourish. Agreement has at last been reached on the names of elements 101–109, in some cases after many years of controversy; proposals for elements 110–112 are about to be considered. The possibility of triple bonding between gallium and transition metals has attracted considerable attention; the first reported Nb–– – Nb triple bond, the first Ti––Te bond, and the shortest iron–iron bond yet structurally determined are less contentious but as remarkable.As well as unusual structural features, other ‘firsts’ continue to be reported, including a molecular TmII complex, primary phosphido complexes of lanthanides, and a remarkable bis(pentalene) compound of thorium.Though not the most abundant of elements, exploration of the chemistry of seaborgium shows it to be similar to Mo and W. Noble metal chemistry provides excellent examples of new potential applications, including a zeolite-encapsulated photoactive RuII complex as a photochemical battery, a homogeneous dehydrogenation catalyst that does not require a sacrifical hydride acceptor, silver chalcogenides with giant magnetoresistance and photochemical energy storage by crystals of an unusual ‘stacked’ gold trimer.Synthetic and structural studies, together with the enormous current interest in reaction mechanisms and bioinorganic chemistry (now routinely making very e§ective use of site-directed mutagenesis) illustrate the vigour and vibrancy of this area of inorganic chemistry.In main group chemistry we have seen the development of novel chiral molecules in which a Group 15 element plays the role of a donor atom. Especially vibrant areas are those in which the molecules contain both nitrogen and phosphorus within a chiral aromatic or ferrocenyl framework. Within Group 16, tellurium continues to exhibit the most impressive array of novel structural types, for example [Te 8 ]2` (isostructural with the long known ions [S 8 ]2` and [Se 8 ]2`) and [Cr 4 (CO) 20 Te 4 ], the organometallic derivative of a Te allotrope.That is not to say that interesting species have not emerged from work with the other Group 16 elements. One fascinating result comes in the form of [NH 4 ] 3 [Ir(S 4 )(S 6 ) 2 ], originally formulated as [NH 4 ] 3 [IrS 15 ] as long as Royal Society of Chemistry–Annual Reports–Book A 11904.The fact that the formulation was so close is testimony to the excellence of the original work. Intriguingly, the fact that the material in question resolves spontaneously upon crystallisation means that enantiomeric crystals were available to the original workers a decade before Werner first separated optically active inorganic complexes.The highlight for 1997 in Noble Gas chemistry must be the confirmation of a Xe–Xe bond. Nineteen years after the reported existence of the dark green Xe 2 ` cation, a structural characterisation of the [Sb 4 F 21 ]~ salt has demonstrated the presence of a Xe–Xe bond which is longer than any other main group element–element bond.Considerable strides have been made in the control of the regio- and stereochemistry of polyaddition of [60]-, [70]- and even [78]-fullerenes, leading to the synthesis of fullerene derivatives with previously unobtainable addition patterns. There has also been a considerable e§ort into the controlled production of carbon nanotube-based materials which has resulted, for example, in the bulk preparation of single-walled carbon nanotubes, bundles of aligned nanotubes, and samples consisting entirely of graphite conical structures.The impressive electromechanical amplifier based on a single [60]fullerene molecule clearly demonstrates the potential of fullerene-based materials in future nanotechnology applications.As far as new solids are concerned, 1997 saw the continued development and sophistication of hydrothermal methods of synthesis, including reports of interesting new alumino- and zinco-phosphates with very low framework densities, and the second report of a 14-membered ring zeolite having circular 10Å diameter channels. More exotic non-oxide systems such as tellurides and nitrides are also beginning to be systematically explored.We also note the work on vanadate anodes with high lithium capacities implying an alternative intercalation mechanism. The high performance of solid oxide fuel cells using a thin film of yttrium-stabilised zirconia and another using doped lanthanum gallates is also noteworthy. 2 F. J. Berry and N. G. Connelly 1 Introduction By F.J. BERRY Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK and N. G. CONNELLY School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK In Volume 94 of Annual Reports, Section A we continue to achieve our aim of covering progress in inorganic chemistry both by Group and by subjects of special interest; this year the special topics are supplemented by a chapter on Mechanisms and Kinetics in the Solid State.All areas of interest to inorganic chemists continue to flourish. Agreement has at last been reached on the names of elements 101–109, in some cases after many years of controversy; proposals for elements 110–112 are about to be considered. The possibility of triple bonding between gallium and transition metals has attracted considerable attention; the first reported Nb–– – Nb triple bond, the first Ti––Te bond, and the shortest iron–iron bond yet structurally determined are less contentious but as remarkable.As well as unusual structural features, other ‘firsts’ continue to be reported, including a molecular TmII complex, primary phosphido complexes of lanthanides, and a remarkable bis(pentalene) compound of thorium.Though not the most abundant of elements, exploration of the chemistry of seaborgium shows it to be similar to Mo and W. Noble metal chemistry provides excellent examples of new potential applications, including a zeolite-encapsulated photoactive RuII complex as a photochemical battery, a homogeneous dehydrogenation catalyst that does not require a sacrifical hydride acceptor, silver chalcogenides with giant magnetoresistance and photochemical energy storage by crystals of an unusual ‘stacked’ gold trimer.Synthetic and structural studies, together with the enormous current interest in reaction mechanisms and bioinorganic chemistry (now routinely making very e§ective use of site-directed mutagenesis) illustrate the vigour and vibrancy of this area of inorganic chemistry.In main group chemistry we have seen the development of novel chiral molecules in which a Group 15 element plays the role of a donor atom. Especially vibrant areas are those in which the molecules contain both nitrogen and phosphorus within a chiral aromatic or ferrocenyl framework. Within Group 16, tellurium continues to exhibit the most impressive array of novel structural types, for example [Te 8 ]2` (isostructural with the long known ions [S 8 ]2` and [Se 8 ]2`) and [Cr 4 (CO) 20 Te 4 ], the organometallic derivative of a Te allotrope.That is not to say that interesting species have not emerged from work with the other Group 16 elements. One fascinating result comes in the form of [NH 4 ] 3 [Ir(S 4 )(S 6 ) 2 ], originally formulated as [NH 4 ] 3 [IrS 15 ] as long as Royal Society of Chemistry–Annual Reports–Book A 11904.The fact that the formulation was so close is testimony to the excellence of the original work. Intriguingly, the fact that the material in question resolves spontaneously upon crystallisation means that enantiomeric crystals were available to the original workers a decade before Werner first separated optically active inorganic complexes.The highlight for 1997 in Noble Gas chemistry must be the confirmation of a Xe–Xe bond. Nineteen years after the reported existence of the dark green Xe 2 ` cation, a structural characterisation of the [Sb 4 F 21 ]~ salt has demonstrated the presence of a Xe–Xe bond which is longer than any other main group element–element bond. Considerable strides have been made in the control of the regio- and stereochemistry of polyaddition of [60]-, [70]- and even [78]-fullerenes, leading to the synthesis of fullerene derivatives with previously unobtainable addition patterns.There has also been a considerable e§ort into the controlled production of carbon nanotube-based materials which has resulted, for example, in the bulk preparation of single-walled carbon nanotubes, bundles of aligned nanotubes, and samples consisting entirely of graphite conical structures.The impressive electromechanical amplifier based on a single [60]fullerene molecule clearly demonstrates the potential of fullerene-based materials in future nanotechnology applications. As far as new solids are concerned, 1997 saw the continued development and sophistication of hydrothermal methods of synthesis, including reports of interesting new alumino- and zinco-phosphates with very low framework densities, and the second report of a 14-membered ring zeolite having circular 10Å diameter channels. More exotic non-oxide systems such as tellurides and nitrides are also beginning to be systematically explored. We also note the work on vanadate anodes with high lithium capacities implying an alternative intercalation mechanism. The high performance of solid oxide fuel cells using a thin film of yttrium-stabilised zirconia and another using doped lanthanum gallates is also noteworthy. 2 F. J. Berry and N. G. Connelly

ISSN:0260-1818    

DOI:10.1039/ic094001

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

1 Introduction 4 2 Alkali and alkaline-earth metals By I. B. GORRELL School of Chemistry, Physics and Environmental Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, UK 2 This report is organized in the same manner as last year and summarizes the main developments in the organometallic and co-ordination chemistry of Groups 1 and 2 published in 1997. In general, compounds with polydentate or macrocyclic ligands have been omitted.The chemistry of alkali-metal electrides has been summarized.1 The syntheses and crystal structures of [LiC(SiMe3)2(SiMe2Ph)(OEt2)], [NaC(SiMe3)(SiMe2Ph)2- (tmen)], [LiCH(SiMe Ph)2]2, and polymeric [RbC(SiMe2Ph)3] and [CsC(SiMe Ph)3] have been reported; all exhibitedM· · ·Ph interactions.2 A series of silyl compounds, [MSiBu53] (M\Li, Na or K) and their complexes, [MSiBu53(L)] (L\ether, amine or aromatic hydrocarbon) have been prepared and structurally characterized, including the crystal structures of [MSiBu53]2, (M\Li or Na), [NaSiBu5 (thf)2]2, [NaSiBu53(pmdien)] and [KSiBu53(C6H6)3].The use of these species as strong bases or reducing agents was also described.3 Polymeric alkali-metal (])-neomenthylcyclopentadienyl complexes [M(g5-C5H4R)] (M\Li, Na or K), [M(g5-C5H4R)L] (M\Na, L\thf;M\K, L\thf or dme) and monomeric [Li(g5- C5H4R)(tmen)] have beenpreparedandcharacterized.4 HighresolutionX-ray powder di§raction has shown MCp (M\Li, Na or K) to form multidecker polymeric structures, with the metals in a linear arrangement forM\Li and Na but zig-zag for K.5 The same technique applied to the alkali-metal phenoxides revealed only one metal environment forM\Li and Na but for M\K, Rb or Cs, two metal environments were observed; one octahedral and the other three-co-ordinate with weak additional M· · · Ph bonding.6 Computational studies suggested that ion-pair interactions influence the geometries, charge distributions, magnetic properties and reaction energies of alkali-metal enolates andphenolates toanequal degree andsophenolatesmay be used as models for enolates.7 2 2], [CaL(thf)3] and [BaL(thf)4] (L\Me2Siflu2) have been re- 3 The structure and bonding of [M(Cp)2]~ (M\Li–Rb) and M(Cp)2 (M\Mg, Ca or Sr) have been studied using density functional calculations.All compounds were predicted to have co-parallel staggered rings, except Ca(Cp)2 and Sr(Cp)2 which have bent structures in agreement with experiment; n-type interactions dominated for the heavier metals.8 The crystal structures of some ansa-fluorenyl sandwich compounds, [Li(thf) ][LiL(thf) 3I.B.Gorrell 4ported.9 A review mentioning lithium and magnesium thiolates has appeared.10 Reductive coupling of dimethylfulvene with alkaline-earth metals yielded inseparable mixtures of the tetramethylethylene-bridged complexes [M(C5H4)2C2Me4] and [M(C5H4Pr*)2] (M\Mg–Ba). However, with phenylfulvene, calcium gave cis- and trans-diphenylethanediyl-bridged ansa-calcocenes.11 The preparations and crystal structures of [M(NSiMe3)2PPh2(thf)n]2 (M\Be or Mg, n\0; M\Ca, n\1; M\Sr or Ba, n\2) have been presented.Interestingly, the anions in the thfcontaining compounds are cisoid. There are M· · · Ph interactions for M\Sr and Ba.12 4 2 3 2 2 2 2 2 2 2 2 2 2 2 3 2 2 2 Lithium Carbon-donor ligands 4 2 4 Reaction of N-benzylbenzamide with a slight excess of LiBu/ produces a deep blue dianion which may be used as a stoichiometric reagent to titrate LiR (R\Me, Bu/, Bu4, Bu5 or aryl).The procedure gives results comparable to those from the Gilman double titration and alkoxides do not interfere.13 The structures of MMe (M\Li or Na) in the gas phase have been determined using millimetre/submillimetre spectroscopy14 and NMR studies led to the identification of [LiBu/(tmen)] as a dimer.15 The structure of [LiCH2CH2Bu5(thf)]4, obtained via cleavage of thf and insertion of the ethylene produced into the C–Li bond of LiBu5, is based on an Li tetrahedron with each face capped by an alkyl ligand.16 The crystal structure of [LiC(SiHMe2)2(OEt2)]2 (OEt2)]2 revealed an SiH · · · Li agostic interaction17 while those of [LiSiMe(Si- PhMe2)2] and [LiSiPh(SiMe3)2] showed Li · · ·Ph contacts with two-co-ordinate lithium atoms.18 A 13C NMR study of partially delocalized allylic lithium compounds, (2-[Mbis(2-methoxyethyl)aminoNmethyl]-1,3-bis(trimethylsilyl)allyl)lithium and (2- [Mbis(2-methoxyethyl)aminoNmethyl]-1-(trimethylsilyl)allyl)lithium, including the dynamics of inversion, 1,3-lithium sigmatropic shifts and the e§ect of pendant groups on the stereochemistry of solvation, has appeared.19 Quantum chemical studies of metal–halogen exchange in the model system LiCH––CH2–MeI were consistent with a T-shaped hypervalent iodine species as the transition state.20 Ether-solvated lithiated 2,6-dimethylstyrene, [Li(L )(2,6-Me2C6H3C––CH2)] (L\OEt2 or OMeBu5) was found to be dimeric in the solid state and in solution.21 The synthesis and characterization of [Li(thf) C(H)––Pmes*(––E)] [E\Nmes* or C(SiMe3)2] have been reported.The structures suggest that incorporation of the lithiated carbon into a heteroallylic n-cloud adds to the stability of phosphonium ylide systems.22 The crystal structure of [LiCH PPh (tmen)] has been redetermined and shown to be dimeric with an (LiCP) ring, rather than monomeric as originally reported.23 The syntheses of [LiCH NRR@]·nthf (NRR@\NMe2, Npip or Mdmpip, n\0; NPhMe, n\2; NPh2, n\1–1.5) have appeared.Recrystallisation of the NPh2 and Npip compounds from hexane–thf yielded [Li (CH NPh2)2(thf)3] and [Li (CH Npip) (thf)2]; both were characterized by X-ray di§raction.24 The syntheses and crystal structures of [Li(CH SMe)(thf)] and [Li (CH SPh) (thf)4] have been reported; the first is a polymeric ladder structure with alternate (LiC) and (LiC) rings and the second is dimeric with an (LiC) ring.25 A theoretical study of the energetics and structures of the 2-lithio derivatives of 1,3-dithiane and 2-phenyl-1,3-dithiane5 Alkali and alkaline-earth metals 2 2 2 7 revealed a high preference for the equatorial orientation as well as a high ionic character for the Li–C bond.26 The crystal structures of [LiC–– –CSiMe2C6H4OMe-4]6 and [LiOCMe2C–– –CH]6 showed n interactions between the Li` cations and the acetylide anions; computational studies were also presented.27 Ab initio calculations also provided evidence of Li–Ph and Li–O chelation for monomeric Z- and E-2- methoxy-1-iodo-1-lithio-2-phenyl-1-alkenes in the gas phase; both were absent in the presence of solvent.28 Crystallographic, spectroscopic and theoretical studies of L4·Li2O·LiOMe·LiOCH2CH2OMe (L\1-methyl-3-lithium-4-tert-butylimidazol-2- ylidene) and [3-lithium-4-tert-butylthiazol-2-ylidene glycoldimethyl ether] show that these compounds are best thought of as carbenes, stabilised by n-donation from adjacent N or S substituents.A related zinc compound exhibited less carbene character.29 Reaction of [LiCH PMe NSiMe3]4 with MCl2 (M\Zn or Co) in toluene in the presence of silicone grease a§orded [Li (CHPMe NSiMe3)3(OSiMe2Bu/)]2, which was crystallographically characterized.30 The NMR spectra of [LiC 2 6H4R-4]n (R\Bu/, Bu5 or SiMe2Bu5) pointed to these species existing as hexamers in solution and the crystal structure of [LiC6H3Bu52-3,5]6 revealed a trigonal antiprismatic array of lithium atoms with six faces capped by aryl groups.These results led the authors to suggest that all alkyl- and aryl-lithium compounds with substituents large enough to prevent intermolecular interactions but not large enough to cause significant crowding are hexameric.31 Following a comparative study of Bu5Cl–Li[R]·~ and LiBu5–R (R\naphthalene), a mechanism for the lithiation of aromatic species has been proposed involving a Bu5·–R donor–acceptor complex.32 Polymer-supported lithium and sodium naphthalenides have been used to prepare lithium and sodium reagents when treated with organic halides, nitriles and phosphates.Reactions proceeded in high yield without production of arene sideproducts.33 The synthesis and reactivity of 1,3,5-trilithiobenzene has been reported.34 NBut H Li(OEt2)2 1 Fluorenyllithium has been found to add to Bu5NCO to yield 9-(N-tert-butylcar boxamido)fluorenyllithium which can be reduced by LiAlH4 to give dibenzo-N-tertbutylaminotoluene on aqueous work-up.This is deprotonated by LiBu/ in ether to give the g5-azapentadienyllithium derivative 1. The deprotonation of 9-(N-tertbutylaminomethyl)fluorene was also investigated and the crystal structures of 1 and the mono-ether adduct of fluorenyllithium (a polymer) together with computational studies were presented.35 A 6Li–13C solid-state NMR study of the tmen complex of solid fluorenyllithium indicated the lithium atom to be positioned centrally above the five-membered ring.36 Studies of topomerization of substituted 9-fluorenyllithiums and a-(benzylthio)benzyllithium in various ethers showed that rates were lower in solvents of bulky molecules and indicated the presence of solvent separated ion pairs in solvents containing small molecules and contact ion pairs in solvents of large mol-I.B.Gorrell 6Fig. 1 Crystal structures of [(LiNPh2)MLiNPh(C6H4Li)N2(LiBu/)2(OEt2)4]. Hydrogen atoms have been omitted for clarity and disorder among the Bu/ and Et groups is not shown (Reproduced by permission from Angew.Chem., Int. Ed. Engl., 1997, 36, 1215) ecules.37A study of the structures and energetics of lithiated cyclopropenyl cations and their acyclic isomers showed that the cyclic isomers are always favoured, but that the acyclic forms became more stable as the degree of lithiation was increased.38 Nitrogen- and phosphorus-donor ligands The surprising product of the reaction of NHPh with a large excess of LiBu/ was 2 found to be [(LiNPh2)MLiNPh(C6H4Li)N2(LiBu/)2(OEt2)4] (Fig. 1) in which twothirds of the amine was dilithiated. Implications for the mechanism of multilithiation were discussed.39 Dimers were usually detected in solutions of lda with a variety of ether and amine ligands, but monomers were observed for trans-N,N,N@,N@-tetramethylcyclohexanediamine or trans-1-dimethylamino-2-isopropoxycyclohexane and monomer–dimer equilibria for 1,2-dipyrrolidinoethane or (2-pyrrolidinoethyl)dimethylamine.40 Dehydrobrominations of (^)-2-exo-bromonorbornane by lda have been investigated.Elimination can occur by deaggregation of disolvated dimers or via parallel pathways involving both mono- and di-solvated monomers. The capacity of di§erent groups to chelate was investigated using series of hemilabile aminoethers.41 Crystallographic and theoretical studies of the e§ect of7 3 2 2 2 3 3 2 2 3 n Alkali and alkaline-earth metals 2 n polydentate donor molecules on lithium hexamethyldisilazide aggregation have shown three- and four-co-ordinate monomers, g1-co-ordinate mono- and di-solvated dimers and polymers of dimers.42 A delicate balance between steric repulsions and aggregation forces was observed in ab initio calculations on 3-N-methylamino-Nmethylpyrrolidine lithium amide and its complex with methyllithium43 and an NMR study of the origin of asymmetric induction by 3-aminopyrrolidine lithium amides has appeared.44 The crystal structures of the aggregates containing LiR (R\Bu/, Bu4 or Bu5) and a chiral lithium amide derived from N-isopropyl-O-methyl valinol have been shown to be based on an Li3N2R ring.45 Lithiation of 1,3-bis(dimethylaminomethyl)- 4,6-dimethyl-2-(trimethylsilylmethyl)benzene with LiBu/ a§orded an aggregate species of the parent lithiated compound and LiBu/ (2: 2) containing a unique (NCNLi2Bu2Li2NCN) ladder framework.46 The synthesis and structure of [LiN(SiMe2CH2NMe2)2] have appeared.In the solid state the compound is dimeric and the two lithium atoms are bridged by the two amido groups with the amine arms of each unit bonded to the opposite lithium centres. In solution a fluxional process interconverted the enantiomeric forms of the dimer units.47 Thermal decomposition of [Li (Me SiNCH2CH2NSiMe3)(thf)2] to a new metastable form of [LiN(SiMe3)2- (thf)] via a 1,4-trimethylsilyl shift has been reported.48 The preparation and crystal structure of [(Me CHN) Si(NLiMe)2] revealed a tetramer based on two (NLiNSi)2 rings connected by two lithium atoms.49 In the solid state agostic CH· · · Li, rather than SiH · · · Li interactions, are observed in [LiMMe Si(H)NBu5N] but in solution two other species with SiH · · · Li contacts are also present. Agostic SiH · · ·Li bonds are found in the solid-state structure of [Mg2MMe2Si(H)NBu5N4]; calculations were also reported.50 The reaction between RNHNHR (R\SiBu5 Me) and LiBu/ a§orded the first monomeric dilithium bis(silyl)hydrazide RNLiNLiR·3thf, the structure of which revealed a bridging thf ligand.51 The N,C-dilithiated derivative of 2-allylpyrrole loses the carbon-bound lithium in hmpa to give a [Li(hmpa)4]` salt.52 In order to prepare [ImNLi]n, ImNH was reacted with LiMe (prepared from MeCl and Li).However, the compound that crystallized from thf was found by X-ray di§raction to be [Li12(O2)Cl2(ImN)8(thf)4]·8thf.53 The crystal structure of N-lithio-N-trimethylsilyl-9- amino-9-borabicyclo[3.3.1]nonane revealed a trimer based on a planar (LiN) ring.54 In the solid state Li[2,6-(NEt2CH2)2C6H3] consisted of dimeric units in which the lithium atoms were bonded to the two ipso-C atoms of the aryl rings and also by intra- and inter-molecular bonds to one amino group of each ligand.55 The preparations and structures of [Li2M2-Me2NCH2-4,6-Me2C6H2N2]·OEt2 and [Li2M2- Me N(Me)NC6H4N2(tmen)] have been reported; both are dimeric in the solid state and in solution.56 The crystal structures of the amidinolithium compound [LiPhNC(Ph)NPh] and its 1: 1 complexes with hmpa, tmen and pmdien as well as the hmpa complex of [LiPhNC(Me)NPh] have been presented; the hmpa species were dimeric, the others monomeric.57 The syntheses and structures of some new di-N,N@- chelating pyridyl and quinolyl-1-azaallyllithium compounds 2 (R1\H, R2\Bu5; R1\SiMe3, R2\Ph) have been reported; dimers are observed unless the lithium is solvated.58 Reaction of 1,3,5-triazine with LiR@ (R@\CHR2, CH2R, Me, Bu/ or Ph; R\SiMe3) yielded 1,4-adducts; however, with LiNR2 or LiCR3·2thf the ring-opened azaheptatrienes [LiMRNC(H)NC(H)NC(H)ERN]n(k-L) (E\N, n\3, L absent or E\CR, n\2, L\thf) were obtained; both were crystallographically characterized.59 The syntheses of the lithium and potassium salts of the8[CH(SiMe )PPh2––NSiMe3]~ anion as well as the synthesis and structure of [LiMCH(SiMe )[Ph(1,2-C6H4)P––NSiMe2]N]2 have been reported.The latter is tricyc- 3 lic with a central Li2N2 ring.60 4 Treatment of the a-lithiated phosphinimine Li[CH(R@)PR2––NSiMe3] with PhCN yielded Li[N(R@)C(Ph)C(H)PR2––NSiMe3] (R@\SiMe3, R\Me or Ph; R@\H, R\Ph); [KMN(H)CPhC(H)PPh2––NSiMe3N(tmen)]2 was obtained from the lithium compound (R\Ph, R@\SiMe3) after partial hydrolysis and was characterized by X-ray crystallography.61 Reaction of [LiN(SiMe3)2·OEt2]2 with C6F5CN yielded a mixture of [LiN(C6F4CN-4)2(thf)2] and (Me3Si)2NC6F4CN-4.The crystal structure of the lithium compound showed the metal to be in a trigonal bipyramidal environment; the apical positions were occupied by a nitrile of an adjacent molecule and by a fluorine atom ortho to the amino nitrogen.62 Dilithiation of 2-Mepy followed by PhCN insertion a§orded [MC5H4N·CHC(Ph)NNLi2]6·4thf, the structure of which revealed an aggregate containing four types of lithium cation and two types of anionic ligand which bind to the metal centres via exclusively Li–N interactions or combinations of C–Li and N–Li bonds.63 Reaction of M[2-(dimethylamino)ethyl]methylaminoNlithium with PhCN gives the new a-amino lithium amide 3 which is a tetrameric cubane in the solid state.A mechanism for the cyclotrimerization of PhCN was suggested.64 Reaction of o-anisaldehyde with LiN(Me)(CH2)2NMe2 a§ords a chiral a-amino lithium alkoxide; in the solid state a racemic tetramer with an open pseudo-cubane core is observed.65 Deprotonation of b-trans-[N (LiO) 4MP(Ph)(CyNH)N4] with LiBu in toluene yields Li4[b-trans-MN4[P(Ph)(CyN)]4N]; in thf and with excess LiBu, the 2 34 4 enolate Li6[b-trans-MN4[P(Ph)(CyN)]4N(CH2––CHO)2]·4thf is formed.The crystal structure of the latter compound exhibited two separated tetradentate co-ordination sites forming concave-shaped cavities.66 Lithiation of 4-isopropylaminopent-3-en-2- one a§orded [(LiOMeCHCMeCNPr*)4], the crystal structure of which revealed an aggregate of Li andO interpenetrating tetrahedra; in solution the chelating terminal nitrogen atoms undergo a fluxional process around each face of the Li tetrahedron; with hmpa [MLiOMeCHCMeCNPr*(hmpa)N2] was obtained.Bond lengths indicated that the iminoenolate form of the ligand predominated. The results led to a rationalisation of the selectivity of dimetallations of enaminones.67 X-Ray- and NMR-data showed that the reaction mixture of [6Li]lithium[2-methoxy-(R)-1-phenylethyl][(S)- 1-phenylethyl]amide and cyclohexene oxide in ether results in the formation of mono- 3 I.B.Gorrell R1 R2 N Me3SiN– Li N PhCN N 49 Alkali and alkaline-earth metals meric and dimeric complexes.The dilithiated amide [6Li]lithium[2-methoxy-(R)-1- phenylethyl][2-([6Li]lithio)-(S)-1-phenylethyl]amide was shown to be dimeric by Xray di§raction. The deprotonation of cyclohexene oxide by these was also investigated.68 The crystal structure of [(Ph PNLi·LiBr)2·4thf]·1.5arene (arene\C6H6 or C7H8) revealed a cubane Li4N2Br2 core; several species were present in solution.69 An improved synthesis together with structural, NMR and ab initio data have been reported for [(LiNPr*) LiCl(tmen)].70 The structure of [MLiN(SiMe 3 2CH2- PPr*2)2N2LiCl], which is based on a three-rung LiNLiClLiN ladder, is maintained in solution.71 The compounds [LiI(bipy) [LiI(bipy)] and [LiI(bipy) solvates of LiI–bipy melts.72 New routes to MCN (M\Li or Cs) via salt metathesis have been reported; the crystal structure of LiCN·0.6dme·0.4dma showed infinite sheets of Li2 units linked end-on by CN~ anions.73 The crystal structures of [LiN(CN) (MeCN) 2 3 2 2 4.5], containing Li(bipy)3`, [LiI(bipy)2], 0.5], a polymer, have been obtained as congruently melting 2] and [LiNC(pyz)] have appeared; both are chain polymers.74 Reaction of [Sb(NMe2)3] with [LiPCy(H)] yielded [Sb(PCy)3]2Li6·6HNMe2·2C6H5Me the structure of which was based on an Sb2P6Li6 core which can be described as a hexameric LiP stack capped at the open (LiP) faces by two Sb atoms.Surprisingly, each lithium atom was co-ordinated by NHMe2.75 The synthesis and crystal structures of the lithium salts of some phosphinoamide anions have appeared.The structures of [Li(PPh NR)(OE2)] (R\CHMe2, CH2CMe3 or 2,4,6-Bu53C6H2) are dimeric for the alkyl derivatives and monomeric for the aryl derivative.76 12 11, 10 9 Oxygen- and sulfur-donor ligands 2 3 2 The syntheses of [LiOR] [R\Pr* or CH(CF3)2] and [LiPb(OR)3] have been reported. The crystal structure of the latter [R\CH(CF3)2] revealed a dimer with two Pb(OR) units bridged by a Li2(k3-OR)2 ring and weak interactions between the benzene solvate and the CF groups; this structure is retained in solution.77 The crystal structures of [LiOSiMe (2-C4H3S)]6 and [LiOCHPr*(2-C4H3S)]6 showed no Li–S (thiophene) contacts; the metal binds to the thiophene n system.78 Tetralithiation of tert-butylcalix[4]arene (H4L) in the presence of wet hmpa yielded Li4L·LiOH·4hmpa, whereas the use of dry hmpa resulted in the isolation of [Li4L·2hmpa]2. The structure of the first was based on a square pyramid of lithium atoms with each face capped by oxygen atoms; that of the second consisted of two square pyramids sharing an edge.79 NMR studies of the thermal and photochemical decomposition of LiBu5–LiOBu5 mixed aggregates to give LiH–LiOBu5 aggregates, Li H(OBu5) and Li H(OBu5) in hydrocarbon solution have been reported.80 The e§ect of OMe solvation on aggregated forms of the lithium enolate of acetaldehyde [(LiOCH––CH2)n(OMe2)x] (n\1–4, x\0–4) has been studied theoretically.The monomer and tetramer were found to be important and the tendency of the lithium cation to reach four-coordination was shown to be less important than is commonly believed.81 The structure of the first lithiated phosphine oxide to contain Li–C bonds has been 2 P(H)––O] a§orded the dimeric diorganophosphinate [(mes) P(O)2Li·2thf]2 and 2 22 2 reported; the structure of [MPh P(O)CHLiC(H)MeEtN4] is based on an Li4O4 cube and each tetrameric unit contains two stereogenic centres.82 Reaction of LiBu/ with [(mes) [(mes) PLi]; the structure of the former showed a planar eight-membered (LiO2P)2 ring.83 Ab initio calculations have shed new light on the possible structure of lithiatedI.B.Gorrell 10 2 6 phosphine oxides in thf and on the factors responsible for the higher stereoselectivity of Horner–Wittig addition reactions.84 Addition of LiBu/ to 1-(N-methylphenylsulfonimidoyl)-2,2-diphenylethene in thf gave rise to a compound containing an eight-membered (LiCSO) ring in which lithium was tetrahedrally surrounded by thf, the sulfoxime (O, N) and the a-carbon.85 The synthesis and crystal structure of a racemic dilithiated S-ethyl-N-methyl-Sphenylsulfoximine cluster with co-ordinated tmen and containing an oxygen-centred Li octahedron has been described.The oxygen was thought to arise from the alkyllithium reagent.86 Reaction of RNSO (R\Bu5 or Me Si) with LiNHBu5 (two 2 3 equivalents) yielded [Li2MOS(NBu5)(NR)N6], the structures of which revealed two di§erent Li12N12O6S6 clusters.The structure for R\Bu5 can be envisaged as resulting from trimerization of Li4S2N4O2 hexagonal prisms through their Li2O2 faces whereas that for R\Me3Si has shown two Li6N6O3S3 cages joined by their Li3O3 faces.87 The structure of [Li4Br3(Et2O)7]` is based on a tetrahedral array of lithium atoms with three faces capped by bromine atoms88 and the crystal structure of LiI(diox) has revealed a linear polymeric structure containing both monodentate and bridging diox ligands.89 The syntheses of the dimers of axial 5-methyl-2-dithiazinyllithium and equatorial 5-methyl-2-dithiazinyllithium-5-borane as well as lithium 5-methyl-2-dithiazinylborate-5-borane have been reported.All are configurationally and conformationally stable.90 The structure of lithium 2,2,6,6-tetramethylpiperidinoselenate revealed a (LiSe) ring with one lithium tetrahedrally co-ordinated (2O]2Se) and the other approximately planar (2N, Se chelating groups).91 2 3 Sodium n A comprehensive study of the preparation, structure, bonding and reactivity of the heavier alkali-metal tris(trimethylsilyl)silanides has appeared.92 The structure of [NaC6H3(mes)2-2,6]2 revealed that the metal centres interact equally with the ipsocarbons of the central phenyl group and those of the mesityl groups.93 Experimental and theoretical techniques demonstrated that sodium salts of carbazole in various ethers form a cation solvation system with a shallow potential and numerous local minima. Three structural types were observed: [cb~Na`L], [cb~Na`L] and [(cb~) NaL] (n~1)~[Na`L]n~1 [L\thf, dme, (MeOCH2CH2)2O, Me(OCH2CH2)3- OMe, Me(OCH2CH2)4OMe, 15-crown-5 or cryptand 221] with the metal co-ordination number in the range 3–7.94 A similar example of structure-determining cation solvation has been provided by a series of solvated sodium salts of the [C HPh 5 4]~ anion.95 The preparations of Na[C5Ph4Bu/], Na[C5H3MC6H4C(O)R-4N2-1,4] (R\Me or C5H11) and Na[C5H(C6H4CH2R-4)4] (R\Me or Pr/) have appeared.96 The syntheses and structures of some sodium phenylhydrazides, including monomeric [Na(Ph)NN(SiMe3)2]·3thf, polymeric (via Na· · ·Ph interactions) [Na(Ph)NN(SiMe3)2]·L (L\thf, Et2O or Bu5MeO) and [Na(H)NNPh2]6, which contained two face-sharing cubes, have been published.97 Solvent-free NaOPh is polymeric in the solid state but crystallises from thf as [NaOPh]6·8thf containing two face-sharing cubes and from tmu as the cubane [NaOPh]4·4tmu.The carboxylation of NaOPh was also investigated with reference to the Kolbe–Schmitt reaction.98 The11 Alkali and alkaline-earth metals 2 2 2)] (M\Na or Cs) have appeared.2 dimers in [NaM(OPPh )(SPPh2)NN(thf)2]2 are based on a Na2O2 ring.99 The preparations and structures of [(Is* SiF)PMSi(CPr*Me The sodium compound is dimeric in the solid state with a puckered tricyclic (FNaPSi) skeleton; in solution a trimer is observed. The caesium compound is polymeric through Cs · · · Ph contacts.100 2 S C – S 4 Potassium, rubidium and caesium 3 2 2 3 A new modification of [KCPh (pmdien)] consisting of zig-zag chains with K· · · Ph interactions, rather than a discrete molecule, has been published.101 The synthesis and structure of [KPhC(H)NC(H)Ph(pmdien)] revealed a polymer containing both g3- CNC and g3-CCC bridging anions.102 Metallation of NH(PPh2)2 with KOBu5 in toluene followed by addition of pmdien yielded [KN(PPh2)2(pmdien)], X-ray analysis of which showed the metal to be surrounded by the chelating triamine, the N-donor amido group and g1- and g2-phenyl groups.103 A series of dihydro-s-triazinidopotassium complexes have been prepared and structurally characterized.Monomeric, dimeric and polymeric potassium potassate structures were observed.104 The crystal structure of [KP(H)mes*] revealed a one-dimensional polymeric ladder with K· · · Ph interactions.105 The potassium enolate [KCH COPh] is bound as an ion pair in [(g5: g1: g1: g1-oepg)ZrMPhC(CH2)ONK(thf)3] and drives the aldol condensation reaction with acetophenone to give [(g5: g1: g1: g1-oepg)ZrMPhC(CH2)2OC(O)C(Me)- PhNK]n; both were crystallographically characterized.106 The synthesis and crystal structure of [KMO(Ph SiO) SiPh2OHN]2·C6H6 have been reported.The molecule was centrosymmetric with the two halves of the dimer linked through a K2O2 ring with two eight-membered potassiotrisiloxanol rings either side.107 The syntheses and crystal structures of [Li(15-crown-5)(SCPh )], [K(18-crown-6)(SCPh3)L0.5] (L\C6H6 or thf), [K(dibenzo-18-crown-6)(SCPh )(hmpa)0.5], [K(dibenzo-18-crown-6)(SCPh3)- 3 6S6 ring by direct K–S bonds and vinylidene-type (C7H8)], [(KSCPh3)6(hmpa)2]·2C7H8, [(KSCPh3)6(C7H8)2] and [(NaSSiPh3)6- (C7H8)2] have been reported.The hexamers, made up of two face-sharing cubes, were stabilised byM· · · Ph (n) interactions.108 The carbene adduct 4 reacted with potassium in thf to give the 1,1-dithiolate, the structure of which was based on a K6S6 hexagonal prism connected to a surrounding K bridges.109 The syntheses and characterization of [MSeC6H3(trip)2-2,6]2 (M\K or Rb) have appeared.X-Ray crystallography revealed M· · · Ph interactions even in the ether adduct of the potassium compound.110 N +N 4 The bis(thf) solvate of 4-n-butyl-4-tert-butyl-2,6-diphenyl-1,4-dihydro-s-triazinido- 1-rubidium exists as a cyclic tetramer in the solid state having a sixteen-membered (NCNRb) ring core.111 The structure of CsCp has been shown by high-resolution 4I.B.Gorrell 123In yielded [Cs(Bz3InCl)]2 which contains a (CsCl)2 ring with the dimers linked by X-ray powder di§raction to be a polymeric zig-zag chain.112 Treatment of CsCl with Bz strong Cs · · ·Ph interactions. Reaction with oxygen gave Cs2[OMBzIn(OBz)2N4] in which the metals are bound in a crown ether fashion with additional weak Cs · · · Ph interactions.113 3 3 2C2H)2(H2O)2] and 2C)2C6H4N], respectively, and the anions [BeM(O2C2H)2N2]2~ and 2C)2C6H4N2]2~ have been prepared.Crystallisation of the latter from 2 5 Beryllium 2 2)] (X\Cl or Br), [BeR(Smes*)(OEt2)], 2, [BeR(NHSiPh3)(OEt2)], [BeRN(SiMe3)2], [BeR(thf)2(k- 3)2(BeCl)2N(SiMe3)2] and Be[(NSiMe3)2CPh]2 2C6H3) have been reported.114 Ab initio calculations for the beryllium 2 3 The syntheses and structures of [BeRX(OEt [BeR(NHPh)] CO)(CO) Mo(Cp)], [PhC(NSiMe (R\2,6-mes carbene complexes, [Be(CX2)n]2` (X\HorF; n\1–4), [BeCl(CX2)n]` (X\HorF; n\1–3), [BeCl (CX2)n] (X\H or F; n\1 or 2) and [BeClMC(NH2)2N3]` showed that the Be–C donor–acceptor bonds were stronger for X\Hand that bond strengths decreased as the number of carbene ligands increased.However, the methylene complexes are less stable than the fluorinated analogues because the C p(n) orbitals of CH remain vacant and are, therefore, more susceptible to nucleophilic attack.115 The preparations of [Be(sal)(OH)], [Be(sal)2], [Be(salNH)2] and [Be(salNR)2] (R\Pr* or Ph) have been reported.X-Ray analysis shows the metal to be tetrahedral for the last two complexes.116 Preparative, potentiometric and NMR studies of the interaction of beryllium(II) with oxalate and malonate have been reported; [BeL(H2O)2], [BeL2]2~, [Be (OH)3L3]3~ and [Be3(OH)3(H2O)3L]` were detected.A crystal structure of the latter for L\malonate revealed tetrahedral beryllium in a Be (OH) ring.117 Beryllium complexes of maleic and phthalic acids [Be(O [BeM(O [BeM(O acetone–water gave the [MeC(O)CH CMe2NH3]` salt which contained beryllium at the tetrahedral spiro centre of two seven-membered rings.118 2 2)2]2, 6 Magnesium Carbon-donor ligands A book on Grignard reagents has been published.119 Ligand exchange reactions between the butadiene compound [Mg(C4H6)(thf)2]n and 1,4-diphenylbuta-1,3-diene, 1,6-diphenylhexa-1,3,5-triene, anthracene, diphenylacetylene and cot a§orded the corresponding magnesium adducts.120 The synthesis and reactivity of 1,4-bis(chloromagnesio)-2,5-di-tert-butylbenzene,a mixture of oligomers, have been reported.121 Nitrogen- and phosphorus-donor ligands The solid-state structures and dynamic solution behaviour of [Mg(NBz [Mg(NBz2)2L]2 (L\thf or hmpa) and [Mg(NBz2)2L2] (L\thf, hmpa or 0.5 tmen) have been described.The base-free compound, containing three-co-ordinate magnesium, is in equilibrium with the monomer in arene solution.122 1,3-Dimethyl-2-13 Alkali and alkaline-earth metals iminoimidazoline formed [(ImNH) 2 4 3 2 2 3 2 Mg]I with MgI2; with Mg(Me)I and MgBu/ the polymers [Mg(ImN)I] and [Mg(ImN)2] were obtained.123 The crystal structures of (Me SiNPMe the tetrahedral complexes [MgI 3)2] and [MgBr1.25I0.75(Me3SiNPMe )(OEt )], and [Mg2I2(Me3SiNPMe2CH2)(Me3SiNPMe2CH2CH(Me)O)(OEt2)] 5, all obtained as by-products from the preparations of [MgX(CH PMe NSiMe3]n (X\Br or I), have been described; the heterocubane [MgBr(NPMe3)]4·C7H8 was 2 2 2 2 2 2 3 2 also presented.124 Reaction of (Me NMe Si)3CI with magnesium yielded [MgIC(Me NMe Si)3] in which all three nitrogen atoms are co-ordinated to the metal and there is a planar carbanionic centre suggesting the absence of a Mg–C bond.125 Reactions between MgR2 (R\Ph, Et or Pr*) and isothiocyanates or carbodiimides in thf a§orded the insertion products [Mg(SCPhNBu5) (thf)2], [Mg(Pr*NCRNPr*)2- (thf)2] (R\Ph, Et or Pr*) and [Mg(Bu5NCEtNBu5)2(thf)2]. The preparations of [Mg2(k-NPr*2)2M(Pr*N)2CNPr*2N2], [MgM(Pr*N)2CNPr*2N2(thf)], [MgMSC(NPh)- NR2N2(thf)2] (R\Et or Pr*) and [Mg2(SCEtNPh)4(OEt2)2] were also reported and several compounds were crystallographically characterized.126 The insertion of some isocyanates and CS into the Mg–Cbonds of polynuclear Al–Mgcompounds has been investigated.127 Reaction of M[P(SiMe3)2]2·4thf (M\Mg–Ba) with PhCN (two equivalents) yields M[P(SiMe )C(Ph)NSiMe3]2·nthf (n\2, M\Mg or Ca; n\3, M\Sr or Ba).128 SiMe3I N Mg PMe2 Me2P NSiMe3 Mg OI OEt2 CH3 5 2 Oxygen- and sulfur-donor ligands 3 Reaction of MgBu with two equivalents of NH(SiMe3)2 followed by addition of Ph2CO yielded crystallographically characterized [M(Me3Si)2NMg[k-OC(H)Ph2]· (OCPh2)N2], whereas reaction of purified Mg[N(SiMe3)2]2 with Ph2CO gave [(Me Si)2N]2Mg(OCPh2)2. The di§erence was attributed to incomplete amination of the MgBu resulting in b-hydride transfer to the ketone.129 The crystal structure of tetrahedral [MgBr(OPh)(OEt2)]2 and its 1: 1 complex with p-isopropylbenzaldehyde have been reported.Interestingly, the ether is not displaced in the latter and the metal is five-co-ordinate.130 Reaction of Mg with methanol a§orded Mg(OMe)2·3.5MeOH, the structure of which revealed a complicated hydrogen-bonded network made up from the cubane [Mg4(k3-OMe)4(OMe)4(MeOH)8], [Mg4(k3-OMe)4(OMe)2- (MeOH)10]2` cations, [(MeO)2H]~ anions and eight non-co-ordinating methanol molecules. Desolvation was discussed.131 Direct reaction of Mg with 1-methoxypropan-2-ol [Mg4(k3-g2-OR)2(k2-g2-OR)4(OR)2] in toluene yielded [R\CH(Me)CH OMe] possessing a centrosymmetric unit with five- and six-coordinate metal atoms.132 The synthesis and characterization of [MgMSC6H3(trip)2- 2,6N2] has appeared110 and reaction of [Tpp-50-]MgMe with PhSeH or Ph2Se2 afforded [Tpp-50-]MgSeH, the crystal structure of which was determined.133I.B.Gorrell 14 3 2 2.136 The crystal structure of [Sr(eg)5]- [Cu(C2H4O2)2]·2eg shows strontium to be co-ordinated by three bidentate and two monodentate eg molecules to give a highly distorted square antiprism. The compound decomposed on hydrolysis and so was unsuitable as a sol–gel precursor.137 The synthesis and structure of [Sr(NH3)8][HP11]·NH3 has appeared.The co-ordination around the metal is described by a square antiprism.138 Compounds prepared via insertion of CS intoM–OEt bonds in ethanol solution have been structurally characterized as [Sr (OCSOEt) (EtOH)8] containing a linear array of eight-co-ordinate metal atoms and [Mg(OCSOEt) (EtOH)4] with an octahedral metal centre.139 Alkaline-earth thiolates M(SR)2 (M\Ca, R\1-adamantyl, Bu5 or CEt3; M\Sr, R\Bu5 or CEt3; M\Ba, R\Bu5) have been prepared from M(NH2)2 and the thiol, either neat or in py solution.The crystal structure of [Sr(SCEt3)2(NH3)py] revealed a chain of Sr2S2 rings linked at Sr with the metal co-ordination number made up to four by the nitrogen bases.Thermal decomposition to MS was also reported.140 5 2 The X-ray di§raction data from Ba[Ph2P(g3-CH2C6H4Me-4)2]2 6 have provided the first crystal structure of a non-metallocene organobarium compound. There are short Ba–C contacts to the ipso and ortho carbon atoms. The bonding is largely electrostatic and the molecule is fluxional in solution.141 Reaction of carbazole with barium in dry thf yielded crystals of [Ba(thf) ][cb]2·thf, the structure of which revealed a pentagonal bipyramidal environment around barium.142 The crystal structures of 7 Calcium, strontium and barium The crystal structure of the first solvent-free p-bonded diorganocalcium compound, Ca[C(SiMe3)3]2 has been reported; the angle at calcium is 149.7(6)°.134 Reaction of Ca[N(SiMe3)2]2·2thf with 6,6-di(cyclopropyl)fulvene yielded bis[Mg5-cyclopropyl- (cyclopropylidene)methylNcyclopenta-1,3-dienyl]bis(thf)calcium.The crystal structure and equilibria involving starting material, product and the amide–cyclopentadienyl intermediate were presented.135 The first structural characterisation of a benzophenone–ketyl complex has been reported; [Ca(hmpa) (OCPh2)2] is trigonal bipyramidal and reaction with Pr*OH followed by hydrolysis yielded Ph CHOH and Ph CO; hydrolysis gave [Ph C(OH)] 2 2 2 3 6 Ph Ph PBa P Ph Ph 3 6 [BaI2(k-H2O)2], [BaI2(k-H2O)(OCMe2)], [BaI2(thf)3] and [BaI2(thf)5]·thf revealed framework, layer, chain and monomeric structures, respectively.The relationships between the structures were discussed in terms of iodine co-ordination number and the solid-state structure of BaI2.143 Reaction of Ba[P(SiMe3)2]2 with PhCN (two equivalents) yielded Ba[N(SiMe )C(Ph)P(SiMe3)]2·nL (L\thf, n\3; L\dme, n\2) containing eight-co-ordinate barium.144 Alkaline-earth b-diketonates (b-diket) continue to attract attention as potential15 Alkali and alkaline-earth metals precursors for CVD.The preparation of [M(b-diket)2L] and [MM(b-diket)2N2L] [M\Mg–Ba; b-diket\tmhd, fod, facac, 1,3-diphenylpropane-1,3-dionate; L\Me(OCH2CH2)nOMe, n\3, 4 or 7] have been reported. The crystal structure of [MCa(facac)2N2MMe(OCH2CH2)7OMeN] showed two Ca(facac)2 units linked by the polyether in an unusual bridging/chelating mode.145 The in situ reaction of [M(OEt) (EtOH)4]n (M\Ca, Sr or Ba) with b-diketones and tmen or pmdien (L) [M(b-diket) resulted in the formation of tight ion pairs, [HL]2 4] (b-diket\1,1,1- trifluoropentane-2,4-dionate or facac).146 The syntheses and crystal structures of [Sr (tmhd) (OSiPh 3 3 2 2 2 3)3]·0.5C6H5Me, which contains a triangular array of metal atoms, and [Sr3MO(SiPh2O)2N3MMe(OCH2CH2)4OMeN2]·0.5C6H5Me, in which the metals are arranged linearly, have been reported.Also prepared from the metal and appropriate silanol or silanediol and base were [M(OSiMe2Bu5)2]n (M\Sr or Ba), [MM[O(SiPh2O)2](H2O)(NH3)xNn] (M\Ca or Ba, x\0.3; M\Sr, x\1), [Sr3MO(SiPh2O)2N3(hmpa)5]·C6H5Me and [Ba3MO(SiPh2O)2N3(hmpa)5(H2O)].147 The calcium b-diketonate complexes [CaL (EtOH)0.5]n·C7H8, [CaL2(HL)], and [CaL(pmdien)] (HL\1,3-diphenylpropane-1,3-dione) as well as [Sr(tmhd) (Htmhd)] have been prepared; the crystal structure of the pmdien complex showed it to be dimeric.148 The synthesis, structure and thermal behaviour of [Ba2Y4(k6-O)(k3- OEt)6(k3-OH)2(tmhd)6]·2EtOH have been reported.149 The crystal structure of [Ba2L4(H2O)1.81] (HL\2-methoxy-2,6,6-trimethylheptane-3,5-dione) revealed the co-ordination number of the metal to be nine.150 References 1 J.L.Dye, Inorg. 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ISSN:0260-1818    

DOI:10.1039/ic094003

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

1 Introduction 2 Reviews The reader is directed specifically to two chapters in Specialist Periodical Reports Organometallic Chemistry (Volume 27) for two reviews complementary to this report. The first review is a comprehensive account of the chemistry of carbaboranes and metallacarbaboranes,2a and the second review is a general account of the organometallic chemistry of Group 13 elements.2b The book Advances in Boron Chemistry summarises the results and advances discussed at the ninth international meeting on boron chemistry (IMEBORONIX) held in Heidelberg, Germany in July 1996; it is divided into 11 chapters and contains 74 articles.2cAspecial edition of Collect.Czech. Chem. Commun. appeared during 1997 to celebrate the 70th birthday of J. Ples¢ek: it contains a number of articles relating to carbaborane, metallaborane and metallacarbaborane chemistry.2d–m Specific review articles2n–u have also appeared on the following topics: ‘Pentafluorophenylboranes: from obscurity to applications’, ‘Boryl metal complexes, boron complexes, and catalytic (hydro)boration’, ‘Recognition of electrondonating guests by carborane supported multidentate macrocyclic Lewis acid hosts: mercuracarborand chemistry’, ‘Semi-sandwich platinum metals metallacarboranes derived fromnido-[C2B9H12]~: chemistry and structural studies’, ‘Main-group-based rings and polymers’, ‘Recent advances in the chemistry of heterocarborane complexes incorporating s- and p-block elements’, ‘Synthesis, structure, and reactions of hydride, borohydride, and aluminohydride compounds of the f-elements’, and ‘Chalcogenoboron hydrides’.3 Boron By M.A. BECKETT Department of Chemistry, University of Wales, Bangor, Gwynedd LL57 2UW, UK This report takes a similar format to that used last year1 and reviews the chemistry of boron compounds reported during 1997. The literature has been surveyed by use of Chemical Abstracts, volumes 126 and 127, in conjunction with independent searches of BIDS and the principal chemical journals.19M.A.Beckett 20 2 2F) was found to generate in yields of 25–37% novel 3.3b Details of the reaction of 3H6(PMe3)2]`, have now been reported; the reaction 4 2 3 Polyhedral species 2]` and twoH2 molecules.3a The reaction between BH3·thf or B2H6 and 2 4H10, B5H9 and B5H11.3f The reaction of Me 2H6, 2Se2 with nido-B10H14 yielded arachno-6,7-k-(MeSe)B10H13 10H13 was formed by the reaction of nido-B10H14 2S3.3g The reaction of B10H14 with PMe2Ph at 200Kresulted in the separable whereas under identical conditions Me2S2 failed to react; however, the analogous thiomethyl derivative 6,7-k-(MeS)B with Me bis(ligand) adducts exo,exo- and exo,endo-6,9-(PMe Ph)2-arachno-B10H12 which were characterised by single-crystal X-ray di§raction studies; the halogenated nido boranes 2-BrB10H13 and 2,4-Cl2B10H12 exclusively gave the exo,endo isomers, and in contrast to the chlorinated product, the brominated products isomerised to the exo,exo isomer upon heating.3h A mixture of products was obtained from the interaction of [NBu ][B10H10] with 2-aminopyridine and the structure of one such product, [PPh4 ][2,9-MN,N@-[2- NH(C5H4N)]NB10H8], was determined by X-ray analysis.3i The reaction of Boranes 2H4(PMe3)2 with [CPh3][BF4], which had previously been shown to yield the The cationic species [BH6]` was readily produced at room temperature in the gas phase under the high-pressure conditions of the flowing afterglow-selected ion flow tube (FA-SIFT) apparatus; the structure of the cation was described as a complex between [BH RCN (R\Me, Et, Bu5 or CH bicyclic carboraza systems related to dihydronaphthalene; these products were in addition to the expected borazines, (RCH NBH) Barachno triborane cation [B proceeded via cluster expansion of [B2H3(PMe3)2]` by reaction with B2H4(PMe3)2.3c The reaction of Bu5BBr with Na–K alloy in toluene yielded a closo derivative, Bu54B4H2, with two bridging H-atoms; the same product was obtained in 74% yield by reduction of Bu54B4 in thf by Na–K alloy followed by protonation by HCl.3d The molecular structure of B4H8(PF3), as determined in the gas phase by electron-di§raction, was shown to be the endo isomer with C symmetry.3e The non-linear pair population analysis was extended to the ab initio SCF closed shell level of theory and this new approach was successfully applied to bonding in the simple boranes B B 3 4 [B10H10]2~ with (SCN)2 in CH2Cl2 gave the thiocyanato derivatives [1- (SCN)B10H9]2~ and [(SCN)2B10H8]2~ which were characterised crystallographically as their bis(tetraphenyl-phosphonium) and -arsonium salts, respectively.3j The crystal structure of [PPh4]2[1,10-(O2N)2B10H8], formed from reaction of [NBu4]2- [B10H10] with [NO2]~ in aqueous MeCN, was also reported.3k The structure of [PPh H][B11H14] had the expected 11-vertex icosahedral-fragment geometry with crystallographically imposed mirror symmetry.3l The synthesis and crystal structures of the ammonia adducts of the closed 10- and 12-vertex species [PPh ][1- 4 (NH3)B10H9] and Cs[(NH3)B12H11] were reported.3m The reactions of closo- [(NH3)B12H11]~ with alkyl halides have been studied in detail; the degree of alkylation of the nitrogen was found to be dependent upon the steric demands of the alkyl groups with four representative compounds characterised by single-crystal X-ray di§raction studies.3n Ring opening of the tetrahydropyran ring of [B12H11O(CH2)5]~Boron 21 Fig. 1 Reduction and oxidation reactions of closo 10- and 20-vertex borane anions (Reproduced by permission from Inorg. Chem., 1997, 36, 5419) 20H18]4~, [a2-B20H18]4~ and [B10H10]2~ to [B20H18]2~ by to produce [B12H11O(CH2)5X]2~ was observed in thf solution for X\F~ orOH~.3o The oxidation of [e2-B organic oxidants was evaluated for general applicability for reactions of polyhedral boranes in non-aqueous systems (Fig. 1).3p 10] 3 2 4 Metallaboranes [(k-H) ter analogue [(k-H) stituted products were obtained from the photolysis of [RuH(CO) presence of PHPh and the structure of [Ru H(CO) (PHPh crystal X-ray di§raction study.4b Metal-rich metallaboranes are reported first.4a,b Hydroboration of [(k-H )Os (CO) by BH3·SMe2 at room temperature yielded the new borylidine cluster analogue 2Os3(CO)9(k-H)2BH] whilst at 65 °C the previously reported ketenylidene clus- 3Os3(CO)9(k3-BCO)] was obtained.4a Mono-, di- and tri-sub- 12BH2] in the 2; spectroscopic data allowed the substitution sites to be assigned 2)2BH2]·CH3CN was confirmed by a single- Boron-rich metallaboranes are considered next.4c–l The preparation and character- 2 2 10N 10 isation of a series of 2-arachno-argenta- and 2-arachno-cupra-tetraboranes were described: solid-state 11B MAS NMR spectroscopy indicated that at room temperature intramolecular boron exchange occurred.4c The directed synthesis of Cr and Mo metallaborane clusters was achieved in the preparations of [(Cp*Cr)2B5H9], [(Cp*Mo)2B5H9] and [(Cp*MoCl)2B4H8] from monoboron fragment sources.4d The product [(PPh3)2(CO)OsB5H9(PPh3)], obtained from the reaction of [(PPh3)2(CO)OsB5H9] with PPh3, had a structure characterised as a nido-osmapentaborane with a pendant BH2·PPh3 group; the degradation of metallahexaboranes to clusters containing pendant boron atoms had previously been suggested from ab initio calculations.4e The dizirconaborane [(Cp Zr)2B5H8][B11H14], exhibiting a novel cluster type, was prepared from the interaction of [ZrCp2Cl2] with two equivalents of Li[B5H8] at low temperature (\[35 °C), followed by exposure to air in CH2Cl2 solution; the reaction proceeded via the [k-2,3-(Cp ClZr)B5H8] stable isolable intermediate.4f The closo hexaborate [B6H6]2~ was observed as a bridging ligand in the co-ordination compounds [M2(k-bis-g3-B6H6)(PPh3)2] (M\Au or Cu) and was characterised by single-crystal X-ray di§raction studies.4g The nido 11-vertex MNiB cages in [(PhCOS) NiB10H8(PPh3)] and [(PPh3)(PhCOS)2NiB10H10]·0.5C6H14 2M.A.Beckett 22 Fig. 2 Molecular structure of [(PMe3)2IrB26H24Ir(CO)(PMe3)2] (Reproduced by permission from Chem. Commun., 1997, 2405) have been synthesised and characterised by X-ray di§raction analyses; both structures displayed ortho-cycloboronation of the thiobenzoates with the formation of fivemembered Ni–S–C–O–B rings.4h,i 2 Macropolyhedral metallaborane chemistry made significant advances during 1997.The 18-vertex species 7,7-(PMe3)2-syn-7-IrB17H20 was obtained in low yield from the thermolysis of (PMe3)2(CO)HIrB8H12 with molten B10H14.4j The 28-vertex cluster with a polyboron core, [(PMe3)2IrB26H24Ir(CO)(PMe3)2] (Fig. 2) was also obtained from this co-themolysis reaction; it was described as a triple-cluster species that consisted of a closo 12-vertex MIrB11N cage and a closo 10-vertex MIrB9N cage fused by a common MIrB2N triangular face with an additional nido 9-vertex MIrB8N subcluster.4k The 21-vertex metallaborane (PMe Ph) HReB20H15Ph(PHMe2) made up of a closo 12-vertex MB12N unit and a nido 11-vertex MB11N unit fused with a common triangular face, and a MReH(PMe Ph) 3 3N fragment capping with three Re–H–B linkages exo to 2Boron 23 2 5 one face of the nido cage, was obtained by reaction of [ReH (PMe Ph)3] with B20H16.4l 2 2 Heteroboranes The reader is directed to a Royal Society of Chemistry publication, Specialist Periodical Reports Organometallic Chemistry for a comprehensive review of the 1997 literature concerning carbaboranes.2a Monocarbaboranes are reported first.5a–d The quenched gas phase reaction between 2 4H10 and allene (CH2CCH2) yielded a fluxional monocarbapentaborane system 4H8 in addition to arachno-1-Me- 4H7.5a Deprotonation occurred at the exo nitrogen atom of nido-7- 2Bu5-7-CB10H12 upon reaction with LiBu/, and addition of [NEt3CH2Ph]Cl gave 3CH2Ph][nido-7-NHBu5-7-CB10H12] which was characterised by X-ray 3)-closo-1-CB9H9 was ob- 3N·BH3 and 6-(NH3)-nido-6-CB9H11 4]; related derivatives of formula 1-L-closo-CB9H9 2S, NH2~ or Me3N) were also reported.5c The computed properties of the nHn`1 (n\4, 9 or 11) radicals and anions were reported and the stability of the 11Me12 radical was seen as remarkable in view of the large predicted ionisation 11H12]~ anion.5d 3 Binvolving arachno-1,3- and arachno-1,2-Me -1-CB 2,5-k-CH -1-CB NH the salt [NEt analysis.5b The monocarbaborane ligand derivative 1-(NH tained in 75% yield from the reaction between Et in thf in the presence of Na[BH (L\Me CB CB potential (4.32 eV) of the [CB Dicarbaboranes are considered next.6a–l Two nido intermediates have been separated, isolated, and characterised by NMR spectroscopy, from the conversion-reaction of arachno-1-carbapentaborane(10) derivatives to closo-pentaethyl-1,5-dicarbapentaborane(5).6a The two-electron reduction of dicarbapentaborane(5) derivatives led to the 4n anti-aromatic five-membered ring compounds, 1,2-diborata-4-boracyclopentadienes.6b The crystal structure of the zwitterionic salt [7,8-(2-SNHC5H5)2-7,8- C2B9H10][CF3SO3] was determined.6c The kinetics of ortho-C2B10H12 formation from acetylenes (propargyl bromide, but-2-yne-1,4-diactate or non-1-yne) and B10H12L2 [L\Me2S, Ph2S, Bu52S, (C6F5)2S, MePhS, Me(C6F5)S or Me(Bu4)S] were investigated in detail: the rate constants decreased with both an increase in the electronegativity and/or an increase in size of substituent on S, and yields also increased as the size and or basicity of the Lewis base increased.6d An improved synthesis and full characterisation of all three 12-vertex C-hydroxycarba-closododecaboranes was reported.6e Two nido anions [7-(4-FC6H4)-7,8-C2B9H11]~ and [7-(4-FC6H4)-7,9-C2B9H11]~ were obtained from closo-1-(4-FC6H4)-1,2-C2B10H11 and closo-1-(4-FC6H4)-1,7-C2B10H11 by interaction with two equivalents of [Bu4N]F in thf or CH CN; the NMR spectra of the initial anionic monoboron product was consistent with the new fluoroborate [HOBHF2]~.6f The compound S––CS2C2B10H10, which displayed a stacked arrangement of the S2C––S moieties in the solid state, was obtained from the reaction of 1,2-(HS) -1,2-C2B10H10 with thiophosgene.6g Parameters have been developed which allow conformational calculations to be carried out on 12-vertex boranes, carbaboranes and their derivatives.6h The functionalisation of o-C2B10H12 with propargylphthalimide or (bromoalkyl)phthalimides and their subsequent conversion into isocyanate-substituted derivatives was reported; the reaction of these isocyanate derivatives towards amino- and alcohol-containing molecules was also described.6i Superacid-promoted polycondensation between bis(4- phenoxyphenyl) derivatives of o- or m-carbaborane and organic dicarboxylic acidsM.A.Beckett 24 2B10H12 Fig. 3 Host–guest interaction of CTV with o-C (Reproduced by permission from Angew.Chem., Int. Ed. Engl., 1997, 36, 504) 3 resulted in linear polyether ketones containing rings and icosahedral carbaborane cages; ‘semi-inorganic’ polymers of molecular weight[150,000 were readily obtained.6j Novel host–guest/inclusion complexes of o-carbaborane with aza- and 7,16- diaza-18-crown-6 macrocycles have been reported and their structures determined by single-crystal X-ray di§raction.6k The inclusion chemistry of o-carbaborane was extended by a report on the complexation reactions with the rigid ‘bowl shaped’ cyclotriveratrylene (CTV) and the symmetrically tris(allyl)-substituted analogue: CTV formed a 2:1 adduct in the solid state but only one of the ligands was found to be bound to the cluster (Fig. 3).6l A few papers appeared during 1997 concerning carbaboranes with more than two carbon atoms.7 Deamination of 7-(Me N)-nido-7,8,9-C3B8H10 led principally to either the parent tricarbollide anion nido-[7,8,9-C3B8H11]~ or to the neutral tricarbaborane, nido-7,8,9-C3B8H12.7a Heating 7-(Me3N)-nido-7,8,9-C3B8H10 or nido- [7,8,9-C3B8H11]~ at 350 °C resulted in rearrangement of the carbon atoms in the cluster open face and produced high yields of the isomeric tricarbollides 10-(Me N)- 3 nido-7,8,10-C3B8H11 and [10-(NMe3)-nido-7,8,10-C3B8H11]~, respectively.7a The 6- trimethylstannyl and 6-triphenylstannyl derivatives of pentaalkyl-2,3,4,5-tetracarbahexaborane(6) were prepared by reaction of the triorganylstannyllithiums with the 6-bromotetracarbaborane derivatives; reactions of the 6-triphenylstannyl derivative towards various electrophiles was studied.7bBoron 25 A few papers appeared during 1997 concerning heteroboranes with heteroatoms other than carbon.8 An improved synthesis of [OB11H12]~ by oxidation of [B11H14]~ with aqueous NaOH was described; the nido-oxaborane anion was obtained in 24% yield and isolated as its tetraethylammonium salt.8a The results of a theoretical investigation of the [OB11H12]~ anion, based on the DFT/GIAO/NMR method, confirmed the nido nature of the cluster with a three-co-ordinate cage oxygen atom.8b Ab initio theoretical studies on all possible isomers of X2B10H10 (X\CH, SiH, N, P or Sb) have been undertaken but a low-energy conventional 1,2 isomer forN was not found; the general trends of stabilities followed the order 1,12[1,7[1,2.8c The structure and bonding characteristics of the dehydro derivative 1,2-Si was compared, with calculations at the HF/6-31-G* and B3LYP/6-31-G* levels of theory, with those of 1,2-dehydro-o-carbaborane and 1,2-dehydrobenzyne; in view of these calculations 1,2-Si 2B10H10 2B10H10 was described as an interesting experimental target.8d 3 3 3 2 Metallaheteroboranes Continuing the tradition of previous years, a survey of the more important developments in metallacarbaborane chemistry is included in this section; a comprehensive review of this area is available elsewhere.2a Metallamonocarbaborane derivatives are described first.9a–f Two novel 10-vertex monocarbon ruthenacarbaboranes 2-Cl-2,5-(PPh3)2-2-H-3,9-(MeO)2-2,1-RuCB8H6 and 2,2-(PPh3)2-2-H-3,9-(MeO)2-2,1-RuCB8H7, and a small amount of the 8-vertex (PPh3)2HRuCB6H4(OMe)3, were obtained from polyhedral contraction by reaction of Cs[nido-B10H12CH] with [RuCl2(PPh3)3] in refluxing methanol; the 10-vertex clusters were regarded as hypercloso species with n rather than n]1 skeletal electron pairs.9a The trinuclear osmium complex/cluster [Os (CO)8(g5-7-NMe3-7-CB10H10)] was synthesised by heating [Os (CO)12] with nido-7-NMe3-7-CB10H12 in bromobenzene; the structure, as established by X-ray analysis, showed the MOsCB10N icosahedral cage, retained the Os triangle, and had two agostic B–H· · ·Os interactions (Fig. 4).9b The closo species 2,2-(PPh tion of [RhCl(PPh synthesis of the salt [Na][Pt(PEt drido complex [PtH(PEt platinamonocarbaborane anion reagent with [AuCl(PPh )], [MCuCl(PPh [HgClPh] yielded dimetallic species.9d Reaction of 5-Me S-6-[(Me Si) 3 3)2-2-H-1-(NMe3)-2,1-RuCB10H10 was synthesised by reac- 3)3] with nido-B10H12CNMe3 under alkaline conditions.9c The 3)2(g5-7-CB10H11)] and its protonation to the hy- 3)2(CB10H11)] was described; metallation of the 3)N4] and 2C––CH]- B10H11 with [MNiCp(CO)N2] a§orded two isomeric 12-vertex cluster derivatives, 10H10 and 1-Cp-2-(Me3Si)2CH-1,2-NiCB10H10; the 1,7 2 3 3 1-Cp-7-(Me Si) CH-1,7-NiCB isomer was characterised by single-crystal X-ray di§raction methods.9e The crystal structures of all three Ag(CB11H6X6) compounds (X\Cl, Br or I) were reported as one-dimensional co-ordination polymers with the hexahalogenocarbaborane anions acting as bridging ligands.9f The tantalum carbaborane complexes [(Et2C2B4H4)CpTaR2] (R\Me or Ph) underwent insertion reactions with nitriles and isocyanides; the thermal and photochemical g2-iminoacyl isomerisation reactions of the isomers [(Et2C2B4H4)CpTaCH3(g2-C,N-CM––NBu5NCH3)] were described.10a The bent-sandwich complex [Li(thf)3][g5-C2B4H4(SiMe3)2][Cp*ZrCl2] was synthesised by reaction of [Cp*ZrCl3] with [C2B4H4(SiMe3)2]2~.10b The synthesis, structures, EPR spectra and reactivities of the bent-sandwich and the half-sandwich titanacar-M.A.Beckett 26 3 Fig. 4 Molecular structure of [Os (CO)8(g5-7-NMe3-7-CB10H10)] (Reproduced by permission from J. Organomet. Chem., 1997, 536/537, 537) 2B4N carbaborane cage systems have been reported. The single-crystal baboranes,10c and the half-sandwich and full-sandwich gallacarbaboranes,10d of the 2,3- and 2,4-MC X-ray di§raction structure of the isonido-metalladicarbaborane 1-H-1,1-(PMe3)2-6- Cl-1,2,4-IrC2B8H9 has been determined and showed a four-membered Ir1-C2-C4-B7 open face.10e The syntheses and structures of hydridoruthenacarbaborane double-decker and triple-decker sandwich complexes [Cp*RuH(Et2C2B4H4)] and [Cp*Co(Et2C2B3- H )RuHCp*] were reported; the monometallic species was characterised crystallog- 3Boron 27 2 Fig. 5 Molecular structure of [CpCoMk5-[(CEt) (BEt) CMe]NCo(S2B6H8)] (Reproduced by permission from Chem. Ber./Receuil, 1997, 130, 329) 2 2 2 raphically.10f The crystal structure of [CpCoMk5-[(CEt2)2(BEt)2CMe]N-7-Co-6,8- (S2B6H8)] (Fig. 5) confirmed the triple-decker arrangement for this complex with the bridging 1,3-diborolyl ring and the terminal thiaborane ligand; the compound was prepared by the three-component reaction of [CpCoMg5-[(CEt) (BEt) CMe]N]~ with CoCl and arachno-[6,8-S2B7H8]~.10g A series of novel bis(cobaltacarbaboranyl), (CoC2B4)2X, dicluster complexes whose apical B7 atoms were linked by organic moieties were prepared by an extension of the ‘recapitation’ method by treatment of 6-vertex nido-MCoC2B3N dianions with monoboron reagents; the characterisation of 7,7@-[Cp*Co(2,3-Et2C2B4H3)]2 and [Cp*Co(2,3-Et2C2B4H3-7)]2X (X\MeCH, CH––CH or C– 22 – –C) were reported.10h Metalladicarbaboranes with the MC -3,1,2-closo-RhC 2B9N cage are reported next.11a–x A series of papers concerning the synthesis, structural characterisation, and reactions of the B8–B8@ bridged derivatives of the bis(1,2-dicarbollido)-3-cobalta(1[) anion,11a–c or the B6–B6@ bridged derivatives of the bis(1,7-dicarbollido)-3-cobalta(1[) anion11c–e were reported.The synthesis and reactivity of the sterically encumbered chargecompensated carbaboranes 7-Ph-11-SMe2-nido-C2B9H10 and 1-Ph-3,3-(CO)2-7- SMe 2B9H8 was described.11f The unique semipseudocloso carbaruthenaborane 1-(PhCC)-2-Ph-3-(cym)-3,1,2-RuC2B9H9, characterised by multinuclear NMR spectroscopy and by single-crystal X-ray di§raction, had a cage geometry between that expected for closo and pseudocloso structures and closer to theM.A. Beckett 28 Fig. 6 Perspective view of the non-icosahedral anion [(CO) C3H5)MoPh2C2B9H9]~ (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 645) 3 2 3 2B9H10]~ and its reaction with 2] to yield 1,1-(PMe2Ph)2-2,4-Ph2-1,2,4-closo-PtC2B9H9 have been 2 2(g3- latter.11g A crystallographic study of [Me N][(CO)2(g3-C3H5)MoPh2C2B9H9] revealed a non-icosahedral closed cage geometry with two four-cage-connected vertices (both occupied by C) and two six-cage-connected vertices (one occupied by Mo) (Fig.6); the cluster contained only one Mo–C connectivity and the two C atoms were substantially separated.11h The related C-monophenyl derivative [BnMe N]- [MMo(CO)2(g3-C3H5)NPhC2B9H10] had the expected icosahedral arrangement con- firmed by a single-crystal X-ray di§raction study.11h Synthetic routes towards the C,C@-diphenyl nido carbaborane [7,9-Ph -7,9-nido-C [PtCl (PMe Ph) described; this compound, with the 1,2,4-MMC2B9N cage geometry, indicated that a hextuple-concerted diamond–square–diamond rearrangement mechanism cannot be operative in the spontaneous isomerisation of 1,2-Ph -3,3-(PMe Ph) -3,1,2-closo- 2 2 2 2 22 2 2B9H11 3)2-3-H-3,1,2-closo-RhC2B9H9-9,12-Br2.11k The first thorium com- 4 2 PtC2B9H9 to 1,1-(PMe2Ph)2-2,8-Ph2-1,2,8-closo-PtC2B9H9.11i The complexes 3-[g1- -3,1,2-closo-RhC SC(H)NPh]-3,3-(PMe Ph) and 2-[g1-SC(H)NPh]-2,2- (PMe Ph) -2,1-closo-RhTeB10H10 have been structurally characterised by X-ray crystallography and described as the first thioformamidate complexes to be isolated.11j A closed icosahedral cage geometry with adjacent Rh and C atoms was found for the cluster 3,3-(PPh plexes incorporating carbollide ligands [Li(thf)4]2[Th(g5-C2B9H11)2X2] (X\Cl, Br or I) and [Li(thf) ][Th(g5-C2B9H11Br3(thf)] were prepared and characterised by a combination of spectroscopic and analytical techniques.11l The molecular structure has been determined of the key catalyst for the hydrogenation of methacycline to doxycycline and epidoxycycline viz.closo-3,3-(g2:g3-C7H7CH2)-3,1,2-RhC2B9H11.11mBoron 29 The palladacarbaborances 1-C4H2RS-3,3-(PMe2Ph)2-3,1,2-PdC2B9H10 and 1- 4H2RS-3,3-(PMe2Ph)2-8-PMe2Ph-3,1,2-PdC2B9H9 (R\Me or H) were obtained 2 2(PMe Ph)2] [7-(C4H2RS)-7,8-nido-C2B9H10]11n The novel bimetallic carbaboranyl haf- 2B9H11)Hf(k,g5: g1-C2B9H11)HfCp*(H)] was ob- 2(g5-C2B9H11)2Hf2Me2] with H2.11o The dinuclear 2(g5-C2B9H11)2Hf2Me2] was found to Cas the major and minor products respectively, from the reaction of [PdCl with Tl nium hydride complex [Cp*(g5-C tained by the reaction of [Cp* hafnium dicarbollide dimethyl complex [Cp* regioselectively dimerise terminal alkynes RC– stituted but-1-en-3-ynes CH C(M\Mo or W), yielded the products [MRu(k-CC CCbaboranes [M(C2B9H11)Mo(k-SPh2)2N2]n~ (n\1 or 2) were prepared by successive oxidation of [(C2B9H11)Mo(CO)2(SPh)2]2~ with Ph2S2 and then PhIO.11r An improved synthesis of [3,3@-Co-(1-R-2-R@-1,2-C2B9H9)2]~ derivatives was reported together with the synthesis of cobaltabis(dicarbollyl) complexes incorporating exo cluster SR substituents.11s The first example of B,C@-bridging in a commo bis(carbollide) complex was observed for [1,8@-k-SEt-3,3@-Co(1-Ph-2-SEt-1,2-C2B9H9)(9@-Ph-1@,9@- C2B9H8)].11t Synthetic routes, structures, and the mechanistic implications involved in the synthesis of mixed cobaltacarbaboranes incorporating g5-pyrrolyl and dicarbollide ligands were reported.11u The synthesis and characterisation of [CoM7- C4H4N(CH2)3-8-Me-7,8-C2B9H9N(g5-NC4H4)], the first structurally characterised molecule with [g5-NC4H4]~ and an organic C–NC4H4 group, was presented.11v Reduction of Cs[Co(1,2-C2B9H11)2] by one equivalent of Na–Hg amalgam yielded the cobalt(II) anion [Co(1,2-C2B9H11)2]2~ which was converted back into the cobalt(III) species by oxidation with 0.5 equivalent of I2; lithiation of the cobalt(III) species followed by reaction with an alkyl halide furnished a new synthetic route to the C-substituted derivatives [Co(RC2B9H10)(C2B9H11)]~ and [Co(RC2B9H10)2]~ (R\Me or C6H13).11w Condensation polymerisation of a cobalt dicarbollide dicarboxylic acid derivative with hexamethylenediamine led to the formation of the first oligomeric amide compounds with cobalt dicarbollide in the main chain.11x There were a number of publications in 1997 relating to metal complexes of substituted dicarbaborane ligands in which the metal remained exo to the cage.12a–g The synthesis of gold(I) and gold(III) complexes with 1-Me-2-SH-1,2-C2B10H10 of the type [Au(SCB10H10CMe)L] (L\PPh3, PPh2Me or AsPh3) or [NBu4]- [Au(C6F5)3(SCB10H10CMe) have been prepared by reaction of the dicarbaborane with suitable gold(I) or gold(III) precursors.12a Crystal structures of the gold(I) complexes related to 1,2-(SH) -1,2-C 2 2 – –CH (R\Me, Pr/ or Bu*) to 2,4-disub- 2––C(R)C–– –CR.11p The complex [Ru(thf)(CO)2(g5-7,8- 2B9H11)], when reacted with the alkylidyne reagents [M(–– –CC6H4Me-4)(CO)2Cp] 6H4Me-4)(CO)4(g5-7,8- 2B9H11)Cp] which readily isomerised to [MRu(CO)4Mp,g5-9-CH(C6H4Me-4)-7,8- 2B9H10NCp].11q Unprecedented tetrathiolate-bridged dinuclear ionic molybdacarhave been reported: [Au2(k- S2C2B10H10)(PPh3)2], [Au2(k-S2C2B10H10)(k-M(PPh2)2(CH––CH)N], [Au2(k- S2B10H10)(k-M(PPh2)2(C6H4)N].12b The synthesis and degradation reactions of the gold(III) complex [Au(S [Au(S X-ray di§raction studies.12c The synthesis and structural characterisation of the novel compound [Au (PPh reported: the molecular structure consisted of a tetrahedral MAu 2B10H10 2B10H10)2]~ was described and the complexes [NBu4]- 2B10H10)2] and [NBu4][Au(S2C2B9H10)(S2C2B10H10)] were characterised by 4M(PPh2)2C2B9H10N2(AsPh3)2], obtained by treatment of 2)2C2B10H10 with [AuCl(AsPh3)] in the molar ratio 1: 2 in refluxing ethanol, was 4N core in which two ofM.A.Beckett 30 Fig. 7 Molecular structure of a small gold cluster with carbaborane ligands: [Au4M(PPh2)2C2B9H10N2(AsPh3)2] (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 993) 2 2B9H10]2~ 2 2 the gold atoms were chelated by the anionic diphosphine ligand and the other two gold atoms were bonded to one arsine ligand each (Fig. 7).12d The gold(III) complex [AuCl2M(PPh2)2C2B9H10N]·CHCl3 contained the expected cis square-planar gold(III) units and the dicarbaundecaborate anion acted as a P,P@-bidentate ligand.12e The S,S@-thioether–thioester chelating ligand [7,8-k-SCH C(O)-7,8-C2B9H10]~ maintained its original cyclic nature upon reaction with [RhCl(PPh)3] in ethanol, but yielded a complex of the transesterified ligand [7-S-8-CH C(O)OEt-7,8-C upon reaction with [PdCl (PPh3)2].12f Structural characterisation of the late transition-metal complexes of bis(o-carbaborane) e.g.[M4~nM(C NiII or CuII), and [CuM(C2B10H10)2N2]2~ have been described and these studies confirmed the structural assignments previously reported.12g 2B10H10)2N2]n~ (M\CoII, Metallaheteroboranes containing more than two cage carbons are reported 3B7H9 [R\H, NCCH2 or MeOC(O)CH2], were prepared from the reacnext.13a–c A series of closo 11-vertex ferratricarbaboranyl complexes, closo-1-CpFe-3- R-2,3,4-C tions of [CpFe(CO)2I] with arachno-[6-R-5,6,7-C3B7H11]~ anions; another isolated product included the first metallapentacarbaborane nido-2-CpFe-7-Me-7,8,9,10,12-Boron 31 10H10)N2]2~ Fig. 8 A PLATON representation of [MHFe(MeSiB (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 888) C5B6H10.13a When a mixture of cyclopentadienyl anions and arachno-[6-(NCCH2)- 5,6,7-C3B7H11]~ were reacted with cobalt chloride, cobaltatricarbaboranes of the general formula closo-1-CpCo-(NCCH2)C3B7H9 along with the unique multimetal cluster commo-Co-[closo-1-Co-8,9-(CpCo) -2,3,5-C3B7H10][closo-2@-Co-3@-(NCCH2- )-1@,10@-C CH 2B7H8] were obtained.13a The synthesis of paramagnetic closo-[1-CpFe- 2-Me-2,3,4-C3B7H9][X] (X\AsF6 or SbF6) salts from nido-[6-Me-5,6,9-C3B7H9]~ and [CpFe(CO)2I] followed by oxidation by AgI, and their antineoplastic bioactivity has been investigated.13bA new route to the tetracarba-nido-octaborane(8) species and the molecular structure of nido-6,9-[Fe(CO) 2 2 10H12]~ with K[BHEt3] and FeBr2 10H10)N2]2~, isolated in 66% yield as its 2 3]2-5,7,8,10-C4H4B4Et4 was described.13c There were a few reports during 1997 of non-carbon containing metallaheteroboranes, although not as many as in previous years.14a–d The closed 10-vertex 1-Et-6,7-Cp* -1,6,7-NRh2B7H7 was isolated in low yield from the reaction between [MRhCp*ClN2], NaH and EtH2NB8H11NHEt in thf.14a The two new isoelectronic nido species k-9,10-(SMe)-8,8-(PPh3)2-8,7-IrSB9H9 and k-9,10-(SMe)-8-(g4-Cp*H)- 8,7-IrSB9H9 have been characterised by single-crystal X-ray di§raction studies.14b The first transition-metal complexes of silaboranes were reported during 1997: thus, the reaction of the sila-nido-undecaborate [MeSiB gave the cluster dianion [MHFe(MeSiB bis(tetrabutylammonium) salt14c (Fig. 8). The sandwich anions [Cp*M(MeSiB10H10)]~ (M\Co, Rh or Ir) were obtained from reaction of the monodeprotonated silaborane with [MCp*MCl2N2].14dM.A. Beckett 32 3 4 Organometallic boron species Pentafluorophenylborane derivatives A review2n relating to the history and recent developments/applications of penta- fluorophenylboranes was alluded to in Section 2, and a number of important publications in this area appeared during 1997. The new compounds [TiCp*Me2E] (E\C6F5 or OC6F5) and [TiCp*Me(OC6F5)2] were found to react with the borane B(C6F5)3 to form the highly electrophilic, thermally unstable, olefin polymerisation initiators [TiCp*Me(E)(k-Me)B(C6F5)3] and [TiCp*(OC6F5)2][BMe(C6F5)3];15a their solution structures and the exchange phenomena of these complexes were also reported.15b The yellow-orange insoluble solid, [MRN(CH2)3NRNTiMe2MB(C6F5)3N], prepared by the reaction of the titanium diamide complex [MRN(CH2)3NRNTiMe2] (R\C6H3Pr*2-2,6) with B(C6F5)3, acted as a catalyst for the living-polymerisation of hex-1-ene.15c Zr(k-MeC Me)B(C Bis(pentafluoro)boron fluoride, which was readily obtained from BF3·OEt2 and two equivalents of C6F5MgBr, was found to react with fluorenyllithium to a§ord (flu)B(C6F5)2, whilst reaction with indenyllithium led to the regioisomers 1- and 2-(ind)B(C6F5)2.15d The cyclopentadienylborane C5H4(SiMe3)B(C6F5)2, underwent smooth dehalogenosilation with [TiCl4] and a§orded [C5H4B(C6F5)2TiCl3] which in the presence of low concentrations of AlEt was active as an ethene polymerisation catalyst.15d The reactions of the so called ‘tuck-in’ permethylzirconocene compounds [Cp*(g5: g1-C5Me4CH2)ZrX] (X\Cl, Ph or Me) with the electrophilic boranes HB(C6F5)2 and B(C6F5)3 produced zwitterionic products which were also olefin catalysts;15e polymerisation [Cp*Mg5- the zwitterionic product, C5Me4CH2B(C6F5)2NZrPh], reacted readily with acetone or acetophenone to yield the stable adducts [Cp*Mg5-C5Me4CH2B(C6F5)2NZrPh(OCMeR)] (R\Me or Ph).15f Bis(propynyl)zirconocene reacted with B(C6F5)3 and gave the C–C coupled [Cp 6F5)3] betaine product.15g 4 2 Heterocycles containing boron 4H4BR)N4] and bis(borole)iodorhodium complexes [[RhI(g5-C4H4BR)2].16b The borirene molecules, (CH)2BH, was identified by FT-IR spectroscopy of a matrixisolation product and density functional theory (DFT) calculations.16a The triple-decker complexes containing borole moieties, [(k-C4H4BR)MRh(g5- C4H4BR)N2] (R\Me or Ph) were readily oxidised by elemental I2 in MePh or CH2Cl2 solution at ambient temperature and produced the heterocubanes [MRh(k3- I)(k5-C The reversible carbonylation and Lewis-base degradations of [MRh(k -I)(g5- C4H4BPh)N4] were reported together with the synthesis and structure of the dinuclear complex [Cp*Rh(k-I) Rh(g5-C 3 was reported and described as the first hetero-p-terphenyl analogue to be structurally characterised.16d Crystallographic evidence for the simultaneous p- and n-donation by a carbonyl group to a divalent boron Lewis acid was obtained by analysis of the structure of Mg6-borabenzene[3-(dimethylamino)acrolein]Nchromium tricarbonyl (Fig. 9); this compound was prepared by B ligand exchange of (g6-borabenzene)(tetrahydrofuran)chromium tricarbonyl.16e The reaction of lithium M[1-(3- 3 4H4BPh)].16c The synthesis and crystal structure of the borabenzene-4-phenylpyridine complexBoron 33 Fig. 9 Crystal structure of Mg6-borabenzene [3-(dimethylamino)acrolein]Nchromium tricarbonyl (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 267) 3 3 dimethylamino)propyl]borabenzeneN with [Mn(CO) (CH CN) ][PF6] a§orded [M1- (3-dimethylamino)propylNborabenzene]manganese(I) tricarbonyl which has an intramolecular N]B interaction in the solid state but which exists in solution in an equilibrium mixture with its ring-opened isomer; 11B NMR spectroscopy was used to measure the equilibrium constants over the temperature range [35 to ]48 °C and allowed an evaluation of *HL– (ca. 25 kJ mol~1).16f 3 The reaction of Li[C5H5BMe] with electrophiles Me3ECl (E\Si, Ge, Sn or Pb) produced the 1,2-dihydroborines 2-(Me3E)C5H5BMe; the crystal structure of the trimethylstannyl derivative showed a long Sn–C bond (228.7 pm) and in solution all derivatives were fluxional with [1,3] sigmatropic migrations of the MMe3EN groups from C2 to C6.16g The borabenzene derivative InMe(C5H5BMe)2 was synthesised from 2-(Me Sn)C5H5BMe and InMe3.16h The complexes [TiCl3(g6-C5H5BMe)], [MMCl3(g6-C5H5BMe)Nx] and [MCl2(g6-C5H5BMe)] (M\Zr or Hf) were obtained 4] (M\Ti, Zr or Hf) and Li[C5H5BMe], 2-(Me3Sn)C5H5BMe, or 2- 3 3 3 from [MCl (Me Si)C5H5BMe in excellent yields; borabenzene complexes were also prepared from the cyclopentadienyl precursors [MCl Cp] (M\Ti or Zr) and [MCl Cp*] (M\Zr or Hf).16i The reaction of two equivalents of Li[C5H5BPh] with [ZrCl4] in Et2) a§orded [ZrCl2(g6-C5H5BPh)2]16j whilst the ethoxyborabenzene complex [ZrCl2(g6- C5H5BOEt)2] was obtained similarly in 71% yield;16k these bis(borabenzene)zirconium(IV) complexes were found to be useful catalysts for a-olefin production.The borabenzene complexes of zirconium(II), [Zr(g6-C5H5BR)2(PMe3)2] (R\NPr*2 or Ph), were prepared and the PMe ligands were found to be easily displaced under very mild conditions.16l The reaction of 1-substituted borepins C 33 3 6H6BX (X\Me, Ph or Cl) with [(py) Mo(CO)] and BF3·OEt2 a§orded the corresponding borepinmolybedum tricarbonyl complexes; reaction of [(g6-C6H6BCl)Mo(CO)3] with appropriate nucleophiles gave the boron-substituted complexes [(g6-C6H6BX)Mo(CO)3] [X\H, OMe, OH, O0.5, NPr*2, NMe2, N(C6H12)2 or NBnMe].16m The relative aromaticity of annelated borepins and related systems has been calculated at the B3LYP/6-311]G** level.16nM.A.Beckett 34 3 2 Fig. 10 Crystal structure of [TiCp (PMe )(HBcatF-3)] (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 1510) 2 2 5 Boration reactions and metal–boryl derivatives Ti(g2-CH 2 3 2 A theoretical study has been undertaken on the mechanism of Pt0-catalysed alkyneand alkene-diboration reactions using the B3LYP density functional method; the observed di§erences between these reactions originated from the energetics of the insertion of the alkyne/alkene into the Pt–B bond.17a In the presence of a catalytic amount of [Pt(dba)2] at 50 °C, bis(pinacolato)diboron added selectively to terminal and cyclic alkenes and provided a route to bis(boryl)alkanes in 76–86% yields.17b Diboron(4) compounds reacted, in the presence of 5 mol% [Pt(C2H4)(PPh3)2] at 80 °C, with a,b-unsaturated ketones and produced the 1,4-addition products.17c Solutions of [Cp* 2––CH2)] catalysed the reaction between ethylene and HBOp (benzo-1,3,2-diazoborolane) and CH2––C(H)BOp was isolated in reasonable (58%) yield at low catalyst loading.17d The synthesis, structure, and reactivity of [TiCp (PMe )(HBcatF-3)] have been reported, and the structure was described as a co-ordination complex involving the B–H bonding pair (Fig. 10).17e The olefin complexes [Cp* M(CH2––CHR)H] (R\H or Me; M\Nb or Ta) reacted cleanly with catecholborane (HBcat) and HBO2C6H3Bu5-4 (HBcat@) to yield [Cp*2M(H2Bcat)] and [Cp* M(H Bcat@)] and the anti-Markovnikov hydroboration products 2 catBCH2CH2R and cat@BCH2CH2R; the solid state structures of [Cp*2Nb(g2- H2BO2C6H3Bu5-3)] and [Cp*2Nb(BH4)] were determined by X-ray di§raction.17f The reaction between the rhodium(III) bis(boryl) complex [RhCl(PPh3)2(Bcat)2] and diborane(4) compounds B2(O2R)2 (O2R\1,2-O2C6H3Me-4, 1,2-O2C6H2Bu52-3,5, and dimethyl-L-tartrate) a§orded the unsymmetrical [RhCl(PPh3)2(Bcat)(BO2R)] and (cat)B–B(O2R) with the possible mechanism involving p-bond metathesis.17g A numBoron 35 2 2 ber of five-co-ordinate ruthenium(II) and osmium(II) boryl complexes Me.g.[M(Bcat)Cl(CO)(PPh3)2] (M\Ru or Os)N resulted from the reactions of [RuHCl(CO)(PPh3)2] or [OsPhCl(CO)(PPh3)2] with the appropriate borane; the new complexes were characterised by IR and NMR spectroscopy.17h Ethyne was found to insert readily into the Ru–B bond of [Ru(Bcat)Cl(CO)(PPh3)2] to form the six-coordinate borylalkenyl complex [RuMCH––CH(BOC6H4O)NCl(CO)(PPh3)2], which was characterised by spectroscopy and by X-ray di§raction methods; the relevance of the observed ethyne insertion for metal catalysed hydroboration reactions was discussed.17i The first low-valent metal complexes containing dialkylboryl ligands have been synthesised: thus, the reaction of the Fischer carbyne complexes [Tp@(CO) M(CR)] (M\Mo, R\p-tolyl; M\W, R\Me or p-tolyl) at room temperature (R\Me) or 60 °C (R\p-tolyl) with the hydroborating agent ‘Et BH’ gave the products [(Tp@)(CO)2MMB(Et)CH2RN] with agostic stabilisation from one H atom of the CH2R group to the metal.17j New borylene complexes of the type [k-BXM(g5- C5H4Me)Mn(CO)2N2] (Mn–Mn) (X\NMe2, Cl, NHBu5, NHPh, OMe, OEt or OH) were prepared by substitution reactions of the metal co-ordinated borylene moiety.17k 2 6 Boron–pnicogen species 2 2 2 6 The molecular structure of (Me2N)2B(NMe)B(NMe2)2, as determined by X-ray diffraction, displayed two-fold symmetry and a planar boron–nitrogen framework.18a (Dimethylamino)bis(trifluoromethyl)borane, (F3C)2B(NMe2), underwent a number of [2]2] cycloaddition reactions withN-sulfinylsulfonamides, aminoiminophosphines, carbodiimides, and a ketenimine and yielded a variety of four-membered heterocyclic ring systems.18b A series of benzo-1,3,2-diphosphaborolanes, C6H4(PR)2BR@ (R\H, Pr* or SiMe3; R@\R2N, R) featuring pyramidal phosphorus atoms with substituents in antiperiplanar positions, were synthesised and characterised by spectroscopic and X-ray di§raction methods; the phosphorus atoms acted as co-ordination sites for the MCr(CO)5N fragment.18c The synthesis of benzo-1,4,2,3-diphosphadiborinane derivatives and benzo-1,5,2,3,4-diphosphatriborepanes were also reported.18c The 1,3,2,4- diphosphadiboretanes were found to be useful starting materials for the e¶cient synthesis of five- and six-membered cage species of the general type [(R NB)2P2E] (E\R NB, R2Si, R2Ge18d or R2Sn18e) and [(R2NB)2P2(E2)] (E2\Me2SiSiMe2).The same methods were extended to the formation of new spirocyclic 9-vertex cages e.g.[(R NB)2P2SiP2(BNR2)2] (R2 N\Pr*2N or tmpip) by reaction of [(Pr* N)BP(H)B(NPr*2)P·Li(DME)] with SiCl4.18f A triple-cage compound [P (Pr* NB)6Si2] (Fig. 11), with 14 atoms in the cage-core, was produced in the reaction of [(Pr* N)BP(H)B(NPr* 2 2 2)P·Li(DME)] with Si2Cl6.18g Addition of one equivalent of BH3·thf to the u-alkenyldiphenylphosphanes H2C––CH(CH2)nPPh2 (n\0–2) gave the corresponding phosphane–borane adducts H2C––CH(CH2)nPPh2·BH3 without further reactions, whilst treatment of the u-alkenyldiphenylphosphanes with 9-borabicyclo[3.3.1]nonane gave the cyclic hydroborated phosphane–borane adducts, (C8H14)B(CH2)nPPh2 (n\3 or 4).18h The phosphane–borane (C8H14)B(CH2)4PPh2, characterised in the crystalline state by X-ray di§raction as a cyclic adduct,18h showed temperature dependent ring-opening and -closure in solution with *HL– of [30.5 kJ mol~1.18i The reactions ofM.A.Beckett 36 6 Fig. 11 Schematic drawing of the triple-cage species [P (Pr* NB)6Si2] (Reproduced by permission from Inorg.Chem., 1997, 36, 1534) 2 2 2 (Me S)BH2Br and (Me2S)BHBr2 with equimolar quantities of 1,2-bis(diphenylphosphino)ethylene (dppee) or 1,2-bis(diphenylphosphino)benzene (dppbn) led to cyclic cationic bis(phosphane)boranes: [LBH ]Br or [LBHBr]Br (L\dppee or dppbn); the bicyclic [L@BH]Br was obtained from the triphosphane [bis(2-diphenylphosphino)phenyl]phenylphosphane (L@).18j 2 2 3 2 1,2-Bis(dimethylamino)-1,2-dibora-[2]ferrocenophane was obtained from the reaction of 1,1-dilithioferrocene with Cl(Me N)BB(NMe )Cl; variable-temperature NMR spectroscopy revealed that a dynamic process in addition to the hindered rotation (*Gt[80 kJ mol~1) about the B–Nbond occurred in solution.18k The highly strained [1]boraferrocenophane [1,1@-Fe(C5H4)2-(k-BN(SiMe3)2] was synthesised from dilithioferrocene·tmen with (Me Si) NBCl2.18l Reaction of the readily available diboryl ferrocenes [1,1@-Fe(C5H4)2(BBrR)2] (R\Br, Me or OEt) with LiPPh2 afforded the ferrocenophanes [1,1@-Fe(C5H4)2-MB(k-PPh2)RN2] (R\Br, Me or PPh2) and [1,1@-Fe(C 2 5H4)2-MB(k-PPh2)OEtNMB(k-PPh2)PPh2N].18m 7 Boron–chalcogen species A series of biborate derivatives of the ‘salen-type’ ligand systems with general formula salenMB(OR)2N2 (R\Me or Et) have been prepared; analogous N,N@-1,n-alkylenebis(3,5-di-tert-butylsalicylideneimine) derivatives were also reported.19a NewBoron 37 of complex metallaboroxide the structure 12 Molecular 2 2 Fig.[CuMO3B2(mes)2N2MLi(CH3CN)(py)N2] (Reproduced by permission from Polyhedron, 1997, 16, 2637) macrocyclic oligoboronate esters have been reported: the reaction of 2,6-pyridinedimethanol with PhB(OH) gave a tetrameric macrocyclic boronate whilst 2-(salicylideneamino)-1-hydroxyethane with PhB(OH) provided a dimeric cycloboronate; both compounds were characterised by single-crystal di§raction methods.19b The controlled hydrolysis of (diorganoamino)dihalogenoboranes substituted with bulky dialkyl or alkyl/aryl groups, resulted in the formation of bis(diorganoamino)dihalogeno-1,3-diboroxanes which were used as ‘building blocks’ for boron heterocyles with the BOB linkage.19c Treatment of CuBr with Li[OB(mes)2] in thf a§orded, after work-up and addition of excess pyridine, the monomeric copper(II) boroxide [CuMO3B2(mes)2N2MLi(CH3CN)(py)N2] (Fig. 12) which contained the new ligand, (mes)B(O)OB(O)(mes), as a result of loss of mesitylene and formation of a B–O–B link.19d A number of 1: 1 adducts of the triarylboroxine (2-MeC6H4)B3O3 with N-donor ligands (4-methylpyridine, cyclohexylamine, pyridine, 3-methylpyridine, piperidine, isoquinoline, and benzylamine) were prepared by reaction of equimolar quantities of amine and (2-MeC temperature; the molecular structures of the related compounds (4-MeC and 4-Mepy·(4-MeC toborane (Tbt)B(SH) followed by treatment with electrophiles such as [Cp TiCl 2 6H4)3B3O3 in Et2O at room 6H4)3B3O3 6H4)3B3O3 were also reported.19e Dilithiation of the dimercap- 2], 2 2M.A.Beckett 38 12 Fig. 13 Molecular structure of the anion [B (BSe (Reproduced by permission from Angew. Chem., Int.Ed. Engl., 1997, 36, 2189) 2 n 3)6]8~ (mes) GeBr2, Ph2SnCl2, (Tbt)SbBr2 resulted in the isolation of novel four-membered 1,3-dithia-2-boretane rings SB(Tbt)SER [ERn\TiCp2, Ge(mes)2, SnPh2 or Sb(Tbt)]; the structures of these ring systems were confirmed in all cases by single-crystal X-ray di§raction studies.19f The novel chalcogenoborate Cs8[B12(BSe3)6] (Fig. 13) was obtained from the reaction of caesium selenide, boron, and selenium by means of a high-temperature solid state synthesis;19g the retention the iscosahedral boron network during such a reaction was highlighted as unusual.19h 3 2 8 Boron–halide species The formation of 1: 1 van der Waals’ complexes between BF and ethene or propene were observed in liquid argon and liquid nitrogen; their IR spectra (4000–400cm~1) were recorded at di§erent temperatures and the complexation enthalpies, *HL–, where calculated to be ca.[8 kJ mol~1.20a Hydrogen bonds and anomeric e§ects were both found to be important in determining the preferred conformations of RR@CO·H BF; MO calculations indicated that these e§ects were ca.[6 and [10 kJ mol~1, respectively, and details should be useful in designing systems which take advantage of such interactions.20b The addition of BX3 (X\Cl, Br or I) to tricarbonylchromium(0) complexes of benzylic alcohols a§orded the analogous benzylic halide complexes in excellent yield.20c The synthesis and characterisation of volatile allylic dihalogenoboranes (R@BX2) were reported; the stability of such compounds in CDCl3 solution was found to be dependent on the halide and ranged from a few minutes (X\Br) to several days (X\F).20dBoron 39 References 1 M.A.Beckett, Annu. 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Farfa� n, J. Organomet. Chem., 1997, 547, 71; (c) W. Maringgele, M. Noltemeyer and A. Meller, Organometallics, 1997, 16, 2776; (d) V.C. Gibson, C. Redshaw, W. Clegg and M.R. J. Elsegood, Polyhedron, 1997, 16, 2637; (e) M.A. Beckett, G. C. Strickland, K. S. Varma, D. E. Hibbs, M. B. Hursthouse and K.M. A. Malik, J. Organomet. Chem., 1997, 535, 33; ( f )M. Ito, N. Tokitoh and R. Okazaki, Organometallics, 1997, 16, 4314; (g) J. Ku� per, O. Conrad and B. Krebs, Angew. Chem., Int. Ed. Engl., 1997, 36, 1903; (h) L. Wesemann, Angew. Chem., Int. Ed. Engl., 1997, 36, 2189. 20 (a) W.A. Herrebout and B. J. van der Veken, J. Am. Chem. Soc., 1997, 119, 10 446; (b) M.D. Mackey and J. M. Goodman, Chem. Commun., 1997, 2383; (c) S.E. Gibson and G. A. Schmid, Chem. Commun., 1997, 865; (d) S. Le Serre and J.-C. Guillemin,

ISSN:0260-1818    

DOI:10.1039/ic094019

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

4 Aluminium, gallium, indiumand thallium By J. P. MAHER School of Chemistry, University of Bristol, Bristol BS8 1TS, UK 1 Introduction This year’s report used a computer search of the ISI physical sciences database, a return to the search method used for 1995 and earlier years. The proportion of references for each element is very similar to that for previous years: aluminium71%, gallium16%, indium 10%, thallium 3%, although this is not the ratio reported here since much interesting chemistry is associated with the heavier elements of Group 13.The reviewis orderedby element, but where the topic concerns more than one element, the review appears with that of the lightest element. In 1886 Charles Hall discovered the electrochemical process for the preparation of aluminiummetal by electrolysis of aluminiumoxide in cryolite at 1000°C.The process was also independently discovered at the same time in France by PaulHe� roult, so that today we have the Hall–He� roult process for aluminium production. The ACS has designated the site of Hall’s discovery in Oberlin, USA (a woodshed laboratory), as a national historical chemical landmark.1 The synthesis of the organometallic fluorides of aluminium, gallium, indium and thalliumhas been reviewed.2 2 Aluminium Blue hydrangea flowers are only produced in rather acid soil, in order to ensure this acidity gardeners have long added aluminiumsulfate to the soil.3 It now appears that both Al3` and Ga3` ions can a§ect the pigmentation directly.Thus aluminium is relatively abundant in plants, so that complexation with anthocyanins could be of biological relevance, and metallic complexation of the anthocyanin catechol moiety is strong enough to induce impressive colour changes from pale red to deep purple.Synthetic anthocyanin models were prepared, and alongside natural anthocyanins from blue flowers of evolvulus pilosus and violet flowers of matthiola incana, the complexation equilibria, thermodynamics and visible spectra were studied.The presence of acyl and malonyl groups seem to be fundamental for the stabilization of the colour in weakly acid conditions.4 The Al3` ion has a strong a¶nity for phosphate oxygens, so that complexes with nucleoside di- and tri-phosphates continue to attract attention. 1H NMR spectra 43(500MHz) for samples that vary in either ADP or ATP concentration and pH, and in the ratio of Al3` to nucleoside phosphate have provided evidence for several Al3`–nucleoside phosphate complexes; the associated formation constants were measured.In neutral solutions the main species present with equal amounts of Al3` and nucleotide are (HO)M 2 L 2 and ML, with excess ligand ML complexes predominate and the bases in these are approximately 87% stacked.5 The active involvement of aluminium in Alzheimer’s disease has been brought into doubt by at least one study.Thus the aluminium concentrations in brain tissue sections from patients for normal and neurofibrillary-tangle-bearing neurons have been examined. Whilst high aluminium levels of up to 500ppm were found in tissue fixed with OsO 4 , with higher concentrations present in neurons than in surrounding tissue, it seems that at least so far as this study is concerned, the aluminium is an artifact introduced during sample preparation.6 The amine phenol ligands H 6 TRNS, H 6 TAMS and H 6 TAPS all form very stable complexes with the stability order GaIII[InIII[AlIII forH 6 TAMSand H 6 TAPS, and GaIII[InIII[AlIII for H 6 TRNS.The solution structures of the complexes were examined by multinuclear NMR (1H, 13C, 27Al, 71Ga and 115In) and by UV spectroscopy; in particular the 1H NMR spectra in D 2 O shows that TAPS has a conformation preorganized for the metal ion complexation. On the other hand the related ligand cis,cis-1,3,5-tris[(2-hydroxy-5 sulfobenzyl)amino]cyclohexane has the wrong conformation for metal ion binding, resulting in slow complexation kinetics and relatively weaker complexation.7 The compound H 2 bped forms complexes with AlIII, GaIII, InIII and with CoIII.The molecular structure of the CoIII complex was determined, showing the CoIII ion to be co-ordinated in a distorted octahedral geometry with N 4 O 2 ligand donors in which carboxylato oxygen atoms are trans and pyridyl nitrogen atoms cis.Formation constants were measured for [M(bped)]` and [M(bped)(OH)] giving respectively, (logK 25 , k\0.16M): M\Al, 10.85, 6.37; M\Ga, 19.89, 15.62; M\In, 22.6, 15.44. For [Ga(Hbped)]2`, logK 25 \21.79. Multinuclear solutionNMR(1H, 13C and 27Al) measurements were made, and these combined with comparison with the solid-state structure of the CoIII complex suggested that the complexes [In(bped)(H 2 O]` and [In(bped)(OH)] contain seven-co-ordinate InIII whilst the gallium complexes are sixco- ordinate with the [Ga(Hbped)]2` complex containing a protonated and uncoordinated carboxylic acid group.The compound [Ga(bped)(OH)] contains a coordinated hydroxide which displaced a carboxylato donor and the [Al(bped)(OH)] complex may be five-co-ordinate.8 The synthesis of the first k-oxo-bridged Group 15 element–aluminium heterodinuclear porphyrins [(oep)(Me)M–O–Al(oep)]ClO 4 (M\P, As or Sb) has been achieved by means of the reaction of [(oep)(Me)M(OH)]ClO 4 with (oep)AlMe.The crystal structure of [(oep)(Me)As–O–Al(oep)]ClO 4 was determined; since the As, O and Al atoms lie on the crystallographic two-fold axis, the As–O–Al bond is explicitly linear.9 The complexes tris(4-phenanthridinolato)aluminium(III) and tris(4-methyl-8- quinolinolato)aluminium(III) form the basis of novel electroluminescent devices, the former is a yellow emitter, the latter is a green emitter.The device structure consists of layers with a glass substrate, indium–tin oxide, a tetraphenyldiamine derivative, AlL 3 complex and Mg–Ag alloy.10 Several interesting aluminophosphate systems have been described, these prepara- 44 J.P. Mahertions are all interesting for their reliance on very clever solution chemistry involving either templates and hydrothermal methods or micelle and gel formations. Such materials are interesting due to their potential use in catalysis.The reaction of aluminium oxyhydroxide with [Co(NH 3 ) 6 ]Cl 3 template, phosphoric acid, and strong aqueous ammonia at 150 °C, gave long orange needles of the novel layered phase [NH 4 ] 3 [Co(NH 3 ) 6 ] 3 [Al 2 (PO 4 ) 4 ] 2 with an [Al 2 (PO 4 ) 4 6~]n lattice.11 A one-dimensional aluminophosphate [C 10 N 2 H 9 ][Al(PO 4 )MPO 2 (OH) 2N] was formed using 4,4@- bipyridine as the template.This forms a structure consisting of a backbone chain containing four-membered rings of AlO 4 and PO 4 tetrahedra with ‘pendant’ PO 2 (OH) 2 groups all held together by hydrogen bonding via bipyridinium moieties.12 The room-temperature synthesis of the hexagonal meso-structured aluminophosphate from an aqueous mixture of aluminium isopropoxide, ethanol, phosphoric acid and strong HF with a surfactant was described.13 Similar thermally stable mesoporous hexagonal aluminophosphates and silicoaluminophosphates have been synthesised based on ion-pair interactions of the aluminophosphate species in the presence of [NMe 4 ]OH and a cationic surfactant [C 16 H 33 NMe 3 Cl].14 Another novel aluminophosphate microporous compound was synthesized from an aqueous aluminophosphate gel at 150 °C in the presence of cyclohexylamine template, this transforms upon calcination above 300 °C into AlPO 4 -5 molecular sieves.This is believed to be a new member of an extra-large pore molecular sieve family, UHM-5.15 Hexagonal, cubic and lamellar aluminoborate mesophases containing octahedral aluminium and tetrahedral boron have been prepared and characterized for the first time.A typical synthesis used sodium dodecyl sulfate as the surfactant, and a 1: 1: 1 mixture of CaO, Al(NO 3 ) 3 and H 3 BO 3 in dilute nitric acid, ammonia was then added to adjust the pH and form a gel which was matured for 48 h.16 Among the more interesting work concerning organoaluminium compounds is the report of the first example of the synthesis ofminacyclopropanes.This synthesis was achieved by a-olefin cyclometallation with EtAlCl 2 in the presence of a chlorine ion acceptor, metallic magnesium and (g5-Cp) 2 TiCl 2 catalyst.17 The reaction of [(Cp*Al) 4 ] with [(Bu5As) 4 ] in toluene gives the polyhedral compound [As 2 (AlCp*) 3 ] which has a D 3) symmetry with three aluminium atoms in the plane and two arsenic atoms at the apices of a trigonal bipyramid.The As–Al bond is 248pm and the Al–Al bonds 283 pm, the latter suggests considerable Al–Al bonding, but since there are only 12 electrons for the nine bonds in the polyhedron framework, the bonding must be similar to that in closo-borane frameworks.18 Another intriguing cluster is that formed from the reaction of trans-[MMe 3 N(H)Al(k-Se)N2 ] with pmdien in toluene to produce a tetranuclear, alane selenide cluster [Al 4 Se 5 (H) 2 (NMe 3 ) 4 ], this molecule consists of an eight-membered ring of alternating Al and Se atoms, with a Se linking across the ring to form two five-membered rings.19 The compound [M(Me 3 Si) 3 CAlMe(k-OH)N2 ·2thf] is the first structurally characterised aluminium hydroxide containing methyl groups, and [M(Me 3 Si) 3 CN4 Ga 4 (k-O) 2 (k-OH) 4 ] which has a heteroadamantane-like core, is the smallest structurally characterised galloxane hydroxide described in the literature.20 The hydrolysis of Al(CEtMe 2 ) 3 in hexane gave the trimeric hydroxide [(EtMe 2 C) 2 Al(k-OH)] 3 , which was converted to the dimer [(EtMe 2 C) 2 Al(k-OH)] 2 upon heating.The reaction of Al(CEtMe 2 ) 3 withH 2 S at room temperature formed the cubane compound [(Me 2 EtC)Al(k3 -S)] 4 , and at 0 °C the hexamer [(Me 2 EtC)Al(k3 - S)] 6 .For the tetramer, there were analogous aluminium compounds with Se and Te, 45 Aluminium, gallium, indium and thalliumand further analogous gallium cubane compounds were prepared.21 The compound [(Me 2 AlOLi) 4 ·7thf·LiCl] is the first structurally characterized aluminoxane stabilized by a separated cation, it is also the first structurally characterized intermediate on the pathway to co-catalytically active methylaluminoxane used in metallocene catalyzed olefin polymerisation reactions.22 Organoaluminiums with O,O@-bifunctional ligands have been cited as organometallic intermediates in C–C bond formation reactions, as catalyst precursors in polymerisations, and as precursors for MOCVD techniques. the reaction of AlMe 3 with ethyl rac-lactate (Helac) gives rac-[Me 2 AlM(S*)-elacN] 2 .Structure investigations in solution and the solid state showed that this adduct is formed in a highly stereoselective manner, and that it is five-co-ordinate and is non-rigid in solution. The compound rac-[Me 2 AlM(S*)-elacN] 2 provides the first evidence for stereoselective association of a dialkylaluminium O,O@-chelate complex.23 Reaction of Et 3 Al with salicyclic acid in a 2: 1 molar ratio results in the formation of the novel tetranuclear compound [Et 2 Al] 4 [(k-O 2 C)C 6 H 4 (k-O)] 2 .The molecule is a centrosymmetric cluster with a framework consisting of one 12- and two six-membered fused heterocycle rings.The two Et 2 Al units symmetrically join the two salicylic acid dianions by bridges between the aryloxide oxygen atom and one carboxylate oxygen atom of the second ligand. The other two Et 2 Al units are chelated by the aryloxide and second carboxylate oxygen atoms of each ligand. The carboxylate groups display bidentate co-ordination with a syn–anti conformation.24 The reaction of [Bu5Al(k3 -O)] 6 with two equivalents of (R,S)-b-butyrolactone gave the aluminoxane, (R,S)-[Al 6 Bu5 6 (k3 -O) 4Mk3 - O 2 CCH 2 C(H)(Me)ON2 ] A, this compound has a molecular structure consisting of two ring-opened lactone moieties inserted into, and bridging, the edge of the Al 6 O 6 aluminoxane.25 The authors concluded that the ring-opening reaction of a b- butyrolactone by an aluminoxane occurs by an attack on the carbonyl group of the lactone by the basic aluminoxane oxo ligands rather than by the alkyl substitutents of the aluminoxane. The observed structure of A, and its activity as a polymerisation catalyst, indicate that the latent Lewis acid mechanism proposed for the ring opening of propylene oxide26 is most likely to be involved in the initiation step in the polymerisation of b-butyrolactone by tert-butylaluminoxane. 3 Gallium The new mineral species gallobeudantite was discovered in Tsumeb, Namibia, and is [PbGa 3 [(AsO 4 ),(SO 4 )] 2 (OH) 6 ], a gallium analogue of the Fe3` mineral beudantite.27 A new gallium oxysulfide, Sr 2 CuGaO 3 S, provides a rare example of square pyramidal gallium, it crystallizes in a layered structure of anti-PbO type Cu 2 S 2 sheets alternating with gallium perovskite oxide layers.28 A single-crystal 71Ga NMR study of the garnet Y 3 Ga 5 O 12 has resulted in the determination of the first chemical shielding tensors reported for the 71Ga quadrupole.there is also a linear correlation between 71Ga and 27Al isotropic NMR chemical shifts.29 The dependences of 71GaNMRchemical shift on concentration, temperature and solvent in various aromatic solvents have been observed for GaBr 3 .30 The presence of hydrogen is necessary for the synthesis of the phase formerly reported as BaGa 6 .Redetermination of the structure by single-crystal X-ray di§rac- 46 J. P. Mahertion and by time-of-flight neutron powder di§raction studies shows that the true formula is Ba 5 Ga 6 H 2 .The unit cell isolated contains slightly distorted gallium octahedra, Ga 6 8~, with barium cations over all edges. The hydride is bound into two types of barium tetrahedra and the stoichiometry is appropriate for a Zintl phase, (Ba2`) 5 (Ga 6 8~)(H~) 2 .31 At 110K the structure of [GaBH 6 ]n consists of helical polymeric chains.32 Gallium nitride continues to attract attention.Gallium nitride nanorods were prepared through a carbon nanotube-confined reaction; Ga 2 O was reacted with NH 3 forming wurtzite structured GaN.33 an alternative synthesis of cyclotrigallazane, [H 2 GaNH 2 ] 3 , which is a precursor to nanocrystalline, phase-inhomogeneous gallium nitride, GaN, has been described.34 The e¶cient preparation of the new polymeric gallium imide MGa(NH)32 Nn from the reaction between [Ga(NMe 2 ) 3 ] 2 and NH 3 at ambient temperatures has been described. TEM and XRD studies show that this gallium imide precursor pyrolyses to a rare cubic–hexagonal variety of GaN.35 Three new alkaline-earth metal gallium nitrides were synthesized as crystals from the elements in sealed niobium tubes at 760 °C using Na–Sr and Na–Ca melts as growth media.The materials are all transparent insulators; yellow Sr 3 Ga 2 N 4 (isostructural with Ba 3 Ga 2 N 4 and Sr 3 Al 2 N 4 ), colourless Ca 3 Ga 2 N 4 (isostructural with Ca 3 Al 2 As 4 and c-Ca 3 Al 2 N 4 ), and orange-yellow Sr 3 Ga 3 N 5 were formed. The latter has a new structure and is one of the few materials prepared from Na melts which has an infinite three-dimensional framework structure.36 A new precursor, tris(neopentyl)gallium, Np 3 Ga, for the growth of GaAs by atomic layer epitaxy (ALE) has been described.Unlike most other alkyl gallium precursors such as Et 3 Ga, which decompose via a b-hydride elimination mechanism, Np 3 Ga undergoes homolysis similar to that of Me 3 Ga, the normal ALE precursor.Carbon incorporation was not significantly reduced compared with Me 3 Ga suggesting that the adsorbed neopentyl radicals undergo decomposition to result in a methyl terminated surface identical to that obtained for growth with Me 3 Ga.37 The system Na`–b-alumina has enormous importance as a solid-state electrolyte, now Ga`–b-alumina has been prepared by ion exchange from Na`–b-alumina, the Ga` ion co-ordination (3]0) shows that it has a stereoactive lone pair.It is stable to oxidation up to 500 °C. The compound GaZr 2 (PO 4 ) 3 was also prepared by ionexchange (Ga` for Ag`) from AgZr 2 (PO 4 ) 3 . X-Ray crystal structure determinations were carried out for both compounds.38 A template synthesis has been applied to produce a novel gallium phosphate.Thus in the presence of propane-1,3-diamine and in water–dmso solvent, a hydrothermal reaction at 150 °C between [GaO(OH)], phosphoric acid, and hydrofluoric acid, gave crystalline [H 3 N(CH 2 ) 3 NH 3 ][GaH(PO 4 ) 2 ]. An X-ray crystal structure determination showed the structure to consist of twisted chains of GaO 4 and PO 4 tetrahedra separated by [H 3 N(CH 2 ) 3 NH 3 ]2` ions.39 The compound Rb 2 [Ga 4 (HPO 4 )(PO 4 ) 4 ]· 0.5H 2 O is a new gallium phosphate, the structure consists of four-, five-, and six-coordinated GaIII ions linked by phosphate groups to form eight-membered rings that hold the Rb` and the water molecules, and which are connected to give rise to infinite channels with eight-membered ‘windows’ along the [100] structure plane.40 The first molecular lithium gallium phosphonate Li 4 [(MeGa) 6 (k3 -O) 2 (Bu5PO 3 ) 6 ]·4thf has been prepared by reaction between tert-butylphosphonic acid and an equimolar quantity of LiGaMe 4 in thf and n-hexane.This is the first molecular ionic gallophosphonate cage 47 Aluminium, gallium, indium and thalliumcontaining co-ordinated Li` ions in the form of a one-dimensional wire, it can be regarded as a potential precursor for the subsequent synthesis of molecular sieves and ion conductors.Conversion to the neutral cubic gallium phosphonate cage [Bu5PO 3 GaMe] 4 was also described.41 A very novel and important anti-malarial compound has been prepared and characterised by X-ray crystallography. The amine–phenol complex [M1,12-bis(2-hydroxy-3- methoxybenzyl)-1,5,8,12-tetraazadodecaneNgallium(III)] is a potent new anti-malarial which selectively targets chloroquine-resistant Plasmodium falciparum.The compound was shown to directly inhibit heme polymerisation in vitro.42 The reaction of Na[MeGa(pz) 3 ] with GaCl 3 leads to the formation of the novel cubane Ga 8 (pz) 12 O 4 Cl 4 ·2thf, and not the expected product [MMeGa(pz) 3N2 Ga]- [GaCl 4 ], this represents the first Ga 4 O 4 core, and so completes the series of gallium –Group 16 heterocubanes.A puzzle for the preparation was the source of the oxygen atoms since reactions were carried out with GaCl 3 in dry thf under argon, it is possible that oxygen comes from traces of air or water entering the reaction.43 The hexadentate ligand N,N@,NA-tris(2-pyridylmethyl)-cis-1,3,5-triaminocyclohexane is related to cis-1,3,5-triaminocyclohexane by the addition of N-pendant 2-pyridylmethyl groups, it forms complexes, [ML][NO 3 ], with gallium(III) and indium( III) which may be useful as radiopharmaceuticals.44 The compounds [TpB65,B65]InSe and [TpB65,B65]InTe are the first structurally characterised indium complexes with a valence multiple bond, they are formed when the complex [TpB65,B65]In reacts with selenium or tellurium.45 Recently, [TpB65,B65]Ga was synthesised,46 and Ga––Se and Ga–– Te compounds made from the corresponding reactions with selenium or tellurium have been characterised.From comparisons with other Ga–Se and Ga–Te bond lengths, the bond lengths (221.4 and 242.8pm respectively) are fully consistent with multiple bonding.47 Selenium insertion into Ga–C and In–C bonds has been employed to synthesise [Np 2 In(k-SeNp)] 2 , [(Me 3 SiCH 2 ) 2 Ga(k- SeCH 2 SiMe 3 )] 2 , [(mes)(4-Mepy)Ga(k-Se)] 2 , and [(mes) 2 (4-Mepy)GaSe(mes)], from the corresponding metal trialkyl compounds.48 The first gallyne, Na 2 [(mes*) 2 C 6 H 3 [Ga–– – Ga[C 6 H 3 (mes*) 2 ] has been prepared by sodium reduction of [(mes*) 2 C 6 H 3 ]GaCl 2 .This is the first example of a gallium with a two-co-ordinate bond, and the first example of a Ga–– – Ga triple bond! There are now several examples of multiply bonded gallium atoms, indeed it seems to be a significant feature of the chemistry of gallium. In this example the Ga–Ga bond length is 231.9(3) pm, being the shortest so far observed.The communication gives a very useful summary of these fascinating materials.49 From the same research group come reports of bis(dimesitylphenyl)gallium bromide with a rare T-shaped co-ordination about the gallium centre [C–Ga–C\153.5(2)°], and (dimesitylphenyl)dimesitylgallium, which probably represents the most sterically crowded trigonal planar gallium aryl so far reported, in this compound the aromatic rings about the GaC 3 plane approach 90°.50 Tris[tri(tert-butyl)silyl]digallanyl, (Bu5 3 Si) 3 Ga 2 , is a new type of compound for a heavy Group 13 element, the gallium is in an oxidation state between I and II and the compound is paramagnetic, giving a complex ESR spectrum with parameters in the same range as those for the related radical anion, [(Bu5 3 Si) 2 Ga–Ga(SiBu5 3 ) 2 ]~.51 The first examples of digallium compounds that feature both organo- and halogenosubstituents, [Li(thf) 4 ][R@(Cl)GaGaCl 3 ] and R@(Cl)GaGa(Cl)R@, have been prepared 48 J.P. Maherby the reaction of Ga 2 Cl 4 ·2(diox) with LiR@ (R@\2,4,6-Bu/ 3 C 6 H 2 ); the Ga 2 Cl 2 skeleton of the latter compound is planar with a dihedral angle of 180°.52 Reactions of yellow tetrakis[bis(trimethylsilyl)methyl]digallane, B, with two equivalents of various carboxylic acids have been studied.Products are formed in which two of the bis(trimethylsilyl)methyl groups are replaced by two carboxylato ligands. An X-ray crystal structure determination showed that the Ga–Ga bond was bridged by chelating carboxylato groups. The Ga–Ga distance was shortened to 238.5(2)pm and the co-ordination number of the Ga atoms increased to four.53 Secondly, B reacted with 1,3-diphenyltriazene to form two compounds.The gallium–gallium bond was retained in the yellow derivative (Ph 2 N 3 )(R)GaGa(R)(N 3 Ph 2 ) 2 [R\CH(SiMe 3 ) 2 ], which was formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the Ga–Ga bond length was 245.79(6) pm.The second product was the orange dialkyl(diphenyltriazenido) gallium derivative R 2 Ga(N 3 Ph 2 ) 3 , where the triazene has reacted as an oxidant by the cleavage of the Ga–Ga bond and probably by release of elemental hydrogen.54 Several interesting tetrameric gallium compounds have been described.The compound [MCp(CO) 2 FeNGaCl 2 ] reacted with E(SiMe 3 ) 2 forming [MCp(CO) 2 FeN4 Ga 4 - E 4 ], (E\S, Se or Te). The crystal structures show that these compounds contain a Ga 4 E 4 heterocubane core with an alternating arrangement of gallium and chalcogen atoms, the galliums are co-ordinated nearly tetrahedrally by three chalcogens and a MCp(CO) 2 FeN group.55 The Ga 4 N 4 skeleton of tetrameric trimethylsilylimidomethylgallane, (MeGa––NSiMe 3 ) 4 is nearly a perfect cube with Ga–N bonds averaging 199pm and Ga–N–Ga angles of 90°.56 Sulfur-bridged cubane-type, aqueous acid soluble, molybdenum–gallium clusters, [Mo 3 GaS 4 ]n` (n\5 or 6) have been prepared from [Mo 3 S 4 (H 2 O) 9 ]4` and gallium metal.The crystal structures of [Mo 3 GaS 4 (H 2 O) 12 ][CH 3 C 6 H 4 SO 3 ] 5 ·14H 2 O and [Mo 3 GaS 4 (H 2 O) 12 ]- [CH 3 C 6 H 4 SO 3 ] 6 ·17H 2 O were determined showing that the Mo–Ga distances are much longer than the corresponding Mo–Mo distances.57 4 Indium Various low-valent indium compounds have been studied.Reaction of indium metal with anhydrous HF and BF 3 resulted in the new InI compound InBF 4 . This forms colourless, transparent single crystals which were shown by an X-ray crystal structure determination to be isotypic to KBF 4 .58 The first characterization of mixed-valent MI/MII compounds has been demonstrated for indium and for thallium by means of the aggregation and redox-disproportionation in tripodal indium and thallium amides. 59 The reaction of indium metal with R 3 PI 2 (R\Ph, Pr* or Pr/) enabled the structural characterisation of the novel ‘subvalent’ indium(II) complex In 2 I 4 (PPr/ 3 ) 2 .Also prepared were the first examples of an indium tertiary phosphine complex which contains an In–In bond; the four- and five-co-ordinate indium(III) complex InI 3 (PPh 3 ) 2 ·InI 3 (PPh 3 ) and the tetrahedral indium(III) complex InI 3 (PPr* 3 ).60 The reaction of indium(I) bromide with a,u-alkanediylbis(bromomercury) complexes (alkane\ butane, pentane or hexane) resulted in the formation of the corresponding a,u-alkanediylbis(dibromoindium) compounds as thf adducts.Displacement of the thf 49 Aluminium, gallium, indium and thalliummolecules by Br~, formed a,u-alkanediylbis(tribromoindate) dianions.61 An organoindium compound with an In 4 S core, isoelectronic to the pentahydrocloso- pentaborate dianion In 4 S[C(SiMe 3 ) 3 ] 4 , has been described.62 The pyridineselenolate (2-SeNC 5 H 4 , SePy) and the 3-(trimethylsilyl)pyridineselenolate [3- (Me 3 Si)-2-SeNC 5 H 4 SePy*] ligands form air-stable indium(III) homoleptic co-ordination compounds In(SePy) 3 and In(SePy*) 3 .These take the form of distorted facoctahedral molecules with chelating SePy ligands.These compounds are useful lowtemperature precursors to the binary selenides. Whilst they sublime intact, thermal decomposition of In(SePy) 3 gives In 2 Se 3 .63 Selenide and selenolate compounds of indium have been the subject of an important comparative study. The reaction of InBu5 3 with selenium gave [(Bu5 2 In)(k-SeBu5)] 2 and [(Bu5In)(k3 -Se)] 4 .The compounds In(CMe 2 Et) 3 and InBu/ 3 reacted with selenium to form [(Me 2 EtC)In(k3 -Se)] 4 and [(Bu/In)(k3 -Se)] 4 , respectively. The reaction of In(CEtMe 2 ) 3 with tellurium formed [(Me 2 EtC)In(k3 -Te)] 4 . The compound [(Bu5In)(k3 -Se)] 4 was also formed from the reaction of [(Bu5 2 In)(k-SBu5)] 2 with either selenium or Se––PPh 3 , while both it and [(Bu5IN)(k-SeBu5)] 2 may be prepared from [(Bu5 2 In)(k-Cl)]n and (Bu5Se)MgCl.The compound [(Bu5 2 In)(k-SeBu5)] 2 may be prepared from [(Bu5In)(k-Cl)] 2 , however, the reaction of [(Me 2 EtC) 2 In(k-Cl)] 2 with (Bu/E)MgCl (E\S, Se or Te) yielded [(Me 2 EtC)In(k3 -E) 4 ]. Reaction of [(Bu5 2 M)(k- Cl)]n (M\In or Ga) with Se(SiMe 3 ) 2 yielded the silylselenolate compounds [(Bu5 2 M)(k-SeSiMe 3 )] 2 .64 The crystal growth of metal tellurides and tellurometallates employing solvothermal reactions below 200 °C resulted in four new indium–tellurium phases, all are Zintl compounds containing novel one-dimensional polymeric chains of (In 2 Te 6 )2~ anions that can be described as alternating fused five-membered rings [(In3`) 2 (Te 2 2~)- (Te2~)], joined at the indium atoms.65 Reaction of ortho-diaminobenzene with InNp 3 gave the tetrameric compound [NpInMk-(NH) 2 C 6 H 4N] 4 , which contained five-co-ordinate indium centres having square-pyramidal geometry and an overall approximate tetrahedral symmetry.66 The tetramer In 4 [C(SiMe 3 ) 3 ] 4 reacted with tricarbonylironcyclooctatetraene to produce a dark red organoindium iron compound, Fe 2 (CO) 6 [In–C(SiMe 3 ) 3 ] 3 , which is one of the very rare examples of a compound with two Fe(CO) 3 fragments symmetrically bridged by three main-group elements, it involves a trigonal bipyramidal Fe 2 In 3 moiety with all indium atoms in equatorial positions.The Fe–In bond lengths are as expected [258.2(2) pm], and the equatorial In–In distance, 364.8(1)pm indicated no significant bonding interaction between indium atoms.67 The first organically templated indium phosphate has been prepared as single crystals from a non-aqueous pyridine–butan-2-ol medium and has a unique twodimensional structure consisting of [Hpy][In(HPO 4 )(H 2 PO 4 ) 2 ]~ layers held together by hydrogen bonding to generate cavities containing the pyridinium cations.68 The compound InI 3 (4-Mepy) 3 has been prepared and characterised by X-ray crystallography. From comparison with the In–I bond distances for a number of related InIII compounds it was found that there is a pronounced relationship between the In–I bond length and the co-ordination number at indium.69 50 J.P. Maher5 Thallium A new monoclinic phase has been observed for superconducting Tl 2 Ba 2 CuO 6`d (Tl-2201).This oxide, Tl-2201, is interesting in that its crystal forms vary from nonsuperconducting to superconducting with T# values up to 90 K, this variation can be achieved by changing the argon annealing temperature for ‘orthorhombic’ Tl-2201 between 200 and 700 °C. Small structural changes can be discerned which add to the evidence for the crucial role of the apical Cu–Obond distance in determining the value of T#.70 Group 13–15 compounds involving thallium are very rare.Thallium indium gallium phosphate semiconductors TixIn 1~yGayP, which are potentially useful as 0.9 to 10 km laser diodes, have been grown by gas-phase molecular beam epitaxy on InP and GaAs substrates. X-Ray di§raction determinations showed the successful growth of TlInP, TlGaP and TlInGaP, although phase separation was observed in TlGaP grown as GaAs.Photoluminescence emission was observed for TlInP and TlInGaP grown on InP.71 The interest in the co-ordination chemistry of thallium hydro(pyrazolyl)borate complexes continues. The hydrotris[3-trifluoromethyl-5-(2-thienyl)pyrazolyl]borato thallium(I) complex, has been prepared. 19F and 203Tl NMR spectroscopy measurements of this revealed an exceptionaly large 850 Hz four-bond J(Tl–F) coupling constant in chloroform, however the coupling constant is highly solvent dependent, and was reduced to 0Hz in methanol, acetonitrile and dimethyl sulfoxide.72 The syntheses and structural characterization of a series of mononuclear dihydrobis(pyrazolyl) borato thallium(I) complexes, Tl[BpB65,R] (R\Me, Pr* or Bu5) were described.The two-co-ordinate TlI centres of Tl[BpB65,R] are supplemented by secondary [Tl · · ·H–B] interactions.73 The new podand ligand hydrotris[3-(2- methoxyphenyl)pyrazol-1-yl]borate (TpA/) has been prepared and the crystal structure of the TlI complex determined, this had a trigonal pyramidal geometry with the three pyrazolyl N-donors, and the lone pair of the TlI ion in the fourth position of the tetrahedron of electron pairs.A weak but significant interaction with one of the anisyl oxygen atoms occurs (Tl · · ·O\301.8 pm), and the displacement of the TlI towards this oxygen atom results in a noticeable trans lengthening of the Tl–N(pyrazolyl) bond to 270 pm, compared with 254pm for the other two Tl–N bonds.74 Reaction of 3-(2-pyridyl)pyrazole with POBr 3 in toluene–NEt 3 gave bis[3-(2-pyridyl)pyrazol- 1-yl] phosphinate (as its triethylammonium salt).The TlI salt of this ligand was shown to be a one-dimensional helical polymer of TlL units, with each ligand bridging two metals and each TlI in a ‘2]3’ co-ordination geometry with two short bonds to ligands (\271 pm) and three longer, weak bonds ([287 pm).As with very many TlI complexes, there is an obvious gap in the co-ordination sphere due to a stereochemically active lone pair.75 Tris[di(4,4@-phenyltriazenido)phenylmethane]dithallium(III) has been prepared. An X-ray crystallographic structure determination showed that each complex contains three doubly deprotonated bis(triazenido) ions and two Tl3` ions. The Tl3` ions are each co-ordinated by three chelating triazenido groups resulting in a trigonal prismatic co-ordination of six N atoms.The Tl–N distances vary between 227 and 239 pm.76 The crystal and molecular structure of the thallium(I) (4-methylthiazol- 51 Aluminium, gallium, indium and thallium2-yl)cyanoximate complex with cis-anti-cis-dicyclohexano-18-crown-6 has been determined.The structure showed seven-co-ordination with a distorted hexagonal pyramidal geometry so that the TlI ion forms close contacts with the six oxygen atoms of the crown ether and the oxygen atom of the oxime group.77 Thallium(I) compounds containing the cyclopentadienyl and electronically related ligands, such as the hydrotris(pyrazolyl)borate ligand have been reviewed. Thallium( I)–arene complexes and alkyl- and aryl-thallium-(I) and -(II) species were also covered and molecular TlII complexes included.78 Improved methods of preparation for CpTl and MeCpTl using ultrasound techniques have been described.79 Two trinuclear gold–thallium–gold complexes, [Tl(C 6 F 5 ) 2 XMAu(C 6 F 5 ) 3 (PPh 2 CH 2 PPh 2 - CH 2 PPh 2 O)N2 ], (X\C 6 F 5 or Cl) in which the phosphine oxide moiety co-ordinates to thallium have been synthesised.80 A heterobimetallic chelate complex bis[2- (dimethylaminomethyl)ferrocenyl]thallium chloride was described.81 The reaction of TlPF 6 with [Re 7 C(CO) 21 ]3~ formed the anion [Re 7 C(CO) 21 (k3 -Tl)]2~.82 The alkylthallium( I) compound has a distorted tetrahedron of Tl atoms in the solid state.83 Bis(g6-toluene)thallium(I)-7,8,9,10,11,12-hexabromo-closo-1-carbadodecaborate is a halogenocarborane-bridged dimer with thallium(I)–arene g6-interactions with two toluene molecules and dative interactions with two Br atoms of one carborane anion and one Br atom of a neighbouring anion.84 References 1 N.C.Craig, J. 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ISSN:0260-1818    

DOI:10.1039/ic094043

出版商:RSC    

年代:1998

数据来源: RSC

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5 Fullerene chemistry By P. R. BIRKETT School of Chemistry, Physics and Environmental Science, University of Sussex, Brighton, BN1 9QJ, UK 1 Introduction Once again there have been a large number of fullerene-based publications covering many fields of research during 1997 and therefore the following are necessarily highlights of those papers. The Nobel lectures of Professors Curl, Kroto and Smalley detailing their accounts of the discovery of the fullerenes are available.1 In addition, a number of special symposia and conference proceedings have been published.2 2 Synthesis, separation and physical properties of fullerenes Aspects of general fullerene science have been reviewed3 and an IUPAC committee has proposed a recommended nomenclature and terminology for fullerenes.4 The extraction, isolation and characterisation of [60]fullerene has been suggested as a safe and reliable separation experiment for school-children to perform.5 The reaction conditions required for the production of fullerenes using both the common ‘Kra� tschmer –Hu§man’ method6 and laser pyrolysis of hydrocarbons such as benzene have been studied further.7 The reversible Diels–Alder cycloaddition of fullerenes with an o-quinodimethane precursor which is used as the Soxhlet extraction solvent can be used to improve the percentage of fullerenes extracted from fullerene-containing soot.8 Single elution of a crude fullerene mixture through a column of poly(dibromostyrene) –divinylbenzene using chlorobenzene as the mobile phase is a simple, fast method for the enrichment of [60]-, [70]- and higher [\100]-fullerenes.9 An IR and 13C NMR study of HPLC fractions of [84]fullerene reveals the presence of five new minor isomers, a D 2 (III) isomer and tentatively D 3$, D 6), C 5 (IV) and either C 5 (V) or C 2 (IV) isomers, in addition to the two, D 2 (IV) and D 2$(II), already characterised;10 the numbering system of the IUPAC system is used here.4 An air-sensitive [119]fullerene dimer containing three tetravalent carbons and two seven-membered rings has been synthesised by either the thermolysis of the dimeric [60]fullerene oxide, C 120 O, or by heating [60]fullerene with [60]fullerene epoxide, C 60 O.11 High resolution ion-mobility measurements and trajectory calculation simulations indicate that C 120 , a [2]2] cycloadduct, is amongst the fullerene clusters produced by laser desorption of fullerene films.12 Moreover, reaction of [60]fullerene with KCN in the solid state using a 55Fig. 1 Coexistence conditions in the density, temperature plane.Fluid densities from mean of liquid and vapour fits. Stars represent liquid–vapour coexistence (Reproduced by permission from Phys.Rev. B, 1997, 55, 2808.) ‘vibrating mill technique’ results in the formation of the fullerene dimer, C 120 , which the crystal structure shows has two [60]fullerene units linked by a cyclobutane ring.13 It has been suggested that it is most appropriate to model fullerenes as polyhedra rather than spheres14 and [240]fullerene is argued to be the most chemically inert fullerene on the basis that the development of faceting in the structure of large icosahedral fullerenes leads to a minimum in the value of the maximum fullerene pyramidalisation angle at this point.15 A total of 61 new enantiomeric pairs of non-spirable fullerenes with less than 1000 atoms all of D 3 symmetry have been identified using a simple six-parameter net diagram approach; in addition the smallest example of an isolated-pentagon fullerene, C 384 , without a spiral is also identified.16 The inner surface of [60]fullerene is calculated to be extraordinarily inert when compared to the convex outer surface using semiempirical calculations on exo- and endo-hedral complexes with reactive molecules such as methyl radicals.17 Highresolution adiabatic scanning of the order–disorder transition of [60]fullerene near 260K finds the transition to be rate dependent even at very slow scanning rates, 100mKh~1, indicating that the [60]fullerene is not in a thermodynamic equilibrium state but behaves as a system with a very long internal relaxation time.18 A full phase diagram has been constructed for [60]fullerene using an isothermal–isobaric molecular dynamics simulation, the liquid phase is found to be unstable at all points within the phase diagram (Fig. 1).19 Total decomposition of high quality sublimed crystals of [60]fullerene after heating at temperatures of 1260K manifests itself by the disappearence of the characteristic [60]fullerene ordering transition at 260K and results in the formation of ‘amorphous carbon’.20 Mass spectroscopy experiments provide evidence that C 2 loss dominates over the loss of C 4 units from the parent C 60 ` in the formation of C 56 `.21 However, two-sector field mass spectrometry reveals that the formation of fragment ions such as C 54 3`, C 52 3` and C 50 3` are formed by the 56 P.R.Birkettevaporation of single C 6 ` units and not by evaporation of C 2 units.22 The bond dissociation energy of neutral [60]fullerene is calculated to be 11.9^1.9 eV by analysis of the rate of delayed ionisation of photoexcited [60]fullerene molecules.23 Irradiation of gas phase [60]- and [70]-fullerenes by 193nm ArF excimer laser results in continuous black-body-type light emission, the internal temperature of the irradiated fullerenes is 2800 K.24 Light emission has also been observed from [60]fullerene under high current density excitation conditions, the light originates at the interface between pristine [60]fullerene and amorphous carbon which is formed slowly during the process and the authors suggest that the reaction products such as highly defective or fragmented fullerene species may be strongly luminescent centres.25 A single twophoton absorption resonance from a [60]fullerene film on a CaF 2 substrate is observed at [2.7 eV and has a coe¶cient of [0.02 cmMW~1 using a degenerate-fourwave mixing technique (DFWM), in addition the third-order non-linear optical susceptibility tensor is approached to its long wavelength limit and found to be at least an order of magnitude larger than theoretical predictions.26 The electronic absorption spectrum of [60]fullerene has been recorded at a temperature of ca. 100K with the spectral range extended down to 450nm for the first time.27 The fluorescence and excitation spectra of [60]fullerene has been re-examined in Ne and Ar matrices, good agreement is found with simulated spectra and an assignment is possible for almost every observed band.28 The laser flash-photolysis study of [60]fullerene particles precipitated from CS 2 and ethanol shows that the results are dependent on the size of the particles studied.29 Electron transfer exists between the photoexcited triplet state of [60]fullerene, TC 60 *, and b-carotene in polar solvents with the quantum yield of electron transfer increasing as the solvent polarity increases.30 The fullerene TC 60 * is quenched in the presence of the hydrogen-bonded phenol–pyridine pair, the process involves electron transfer from the phenol to the triplet [60]fullerene concerted with proton transfer of the bonding proton to the pyridine.31 [60]Fullerene can be selectively reduced to its anions,C 60 n~ (n\1 or 2), both are inert to water and by oxidation of the C 60 2~ with oxygen it is possible to form an aqueous colloidal solution of [60]fullerene.32 Similarly colloidal dispersions of [60]fullerene in water have been prepared, have negatively charged surfaces and are polydispersed with a wide range of sizes.33 The peculiar temperature dependence of the solubility of [60]- and [70]-fullerenes in common organic solvents has been ascribed to the formation of aggregates of fullerenes which begin to precipitate as the concentration rises to a maximum.34 [60]Fullerene chemically bonded to silica has been used as a stationary phase for liquid chromatography and separates polycyclic aromatic hydrocarbons and [60]- and [70]-fullerenes e¶ciently.35 The flow microcalorimetry method shows that at low [60]-fullerene surface coverage a strong irreversible adsorption occurs othe active carbon substrate used which produces a large molar integral enthalpy e§ect, higher coverages produce a weaker reversible e§ect which dominates the process.36 High microscopic friction is found for [60]fullerene thin films in comparison to medium friction for amorphous carbon and diamond and very low friction for graphite.37 An investigation of [60]fullerene as a jet fuel deposit inhibitor reveals that the fullerenes photosensitised the fuels towards formation of high levels of hydroperoxides rather than inhibiting deposition of waste material.38 Fullerenes have been converted to diamonds using shock compression,39 in one report fullerene nanotubes are found to 57 Fullerene chemistryFig. 2 Schematic diagram of the electromechanical single-molecular amplifier.The magnified section shows a single [60]fullerene molecule electrically connected between an STM tip and a surface; V IN actuates a piezoelectric translator and the output signal is V OUT (Reproduced by permission from Chem.Phys. Lett., 1997, 265, 353.) produce a better diamond nucleation rate than [60]fullerene on Si substrates.39c Superior plasma-etch-resistance to resist films is produced by [60]fullerene when compared with other additives.40 A fullerene-based device has been developed as the first single-molecule electromechanical amplifier (Fig. 2). The device is based around the STM, uses a single [60]fullerene molecule and works on the principle of modification of the tails of the LUMO and HOMO wavefunctions close to the Fermi level by molecular mechanical deformation which is achieved by piezoelectric actuation, an amplification factor of five is currently achievable.41 An NMR study of the heterofullerene, (C 59 N) 2 , and two of its monomeric derivatives, C 59 HN and C 59 (CH 2 Ph)N allows the following assignments to be made: carbon atoms a to theNatom lie in the region d 155–156, 124–125 (b, adjacent to sp2), 135–138 (b, adjacent to sp2) and 144–149 (b, adjacent to sp3).42 Photolysis of (C 59 N) 2 leads to the formation of the azafullerene radicals43a and the calculated spin density is located in the main at the a carbon position.43b The gas-phase electron di§raction spectrum of [70]fullerene shows that the equatorial diameter of the ellipsoid is 7.178(50)Å and does not support the ‘pinching in’ of the molecule at its equator in contrast to condensed-phase electron di§raction work.44 The Raman excitation profiles of [70]fullerene have been constructed for the most intense resonance Raman bands and symmetry assignments made and as a consequence [70]fullerene has been suggested as a good model for future studies of higher 58 P.R. Birkettfullerenes due to its lower symmetry and more localised molecular orbitals.45 The electron a¶nities of twenty-one higher fullerenes, including [72]- and [74]-fullerenes, have been obtained using the ion/molecule equilibria method.46 [76]Fullerene has been studied using laser flash photolysis and the lifetime of the singlet excited state of [76]fullerene is estimated to be 1.7 ns.47 The higher fullerene radicals, C 76 ·~, C 78 ·~ and C 84 ·~, have been electrochemically generated under both moisture- and oxygenfree conditions and observed using EPR spectroscopy.48 Pulse radiolysis studies have revealed that electron transfer occurs from [76]- and [78]-fullerenes to radical cations of various arenes and provides evidence for the Marcus inverted region (the range in which the rate constants decrease with increasing free energy toward the highly exothermic region).49 The symmetry and shape of five of the isomers of [78]fullerene are found to have a distinct e§ect on the third-order non-linear spectra by extended Su–Schrie§er–Heeger (SSH) and the sum-over-state (SOS) calculations.50 The vapour pressure of [84]fullerene has been measured and the sublimation enthalpy at 950K found51 to be 210^6 kJ mol~1and four-wave-mixing measurements reveal that the second hyperpolarisability of [90]fullerene is approximately eight times that of [60]- fullerene.52 The discussion regarding the presence of fullerenes in meteorites and space continues.The gaseous products evolved from the UV irradiation of solid hydrogenated amorphous carbon (HAC) produces a range of products, including fullerenes; the authors suggest that the data shows that the decomposition of HAC in interstellar shocks may be a source of fullerenes.53 Calculated molecular abundances for homogeneous dense interstellar clouds have been produced and [60]fullerene found to rise to a maximum abundance at a steady state.54 Earlier observations of [60]- and [70]-fullerenes in the Allende meteorite have been reconfirmed although they are now detected in much lower concentrations,55 however, Heymann56 finds that there are no fullerenes present in the Allende meteorite using similar spectroscopic techniques.It has been proposed that two new di§use interstellar bands (DIBs) in the near-infrared are consistent with experimental measurements of the [60]fullerene cation, C 60 `, in the laboratory, suggesting that fullerenes play an important role in interstellar chemistry. 57 However, it also reported that the measured bands will be slightly di§erent in the gas phase and that the two main lines of the spectrum of the DIBs di§er significantly from those of the known laboratory data of C 60 ` and therefore the assignment of the DIBs to C 60 ` is incorrect.58 More information is becoming available about the biological properties of [60]- fullerene and its derivatives (also see Section 4).For example, [60]fullerene inhibits the replication of simian immunodeficiency virus (SIV) in vitro and the activity of Moloney murine leukaemia virus (M-MuLV) reverse transcriptase.59 An HPLC assay of [60]- fullerene in the blood, the liver and the spleen has been developed using either photodiode detection or mass spectrometry after intraperitoneal administration of a micronised [60]fullerene suspension.60 3 Endohedral fullerenes A review describing possible approaches to the synthesis of endohedral metallofullerenes has been published61 and general reviews of endohedral metallofullerenes are 59 Fullerene chemistryalso available.62 Endohedral alkali-metal fullerenes have been synthesised by the irradiation of thin films of [60]fullerene with an ion beam of appropriate energy, the resultant films contain up to 50% Li@C 60 , are stable in air and can be sublimed.63 The Li-implanted thin films have been extracted with CS 2 and three well defined peaks are observed using HPLC.Separation produces two endohedral Li species, one is Li@C 60 , the other may be the endohedral fullerene dimer, Li@C 120 .64 The Raman and FTIR spectra of the lithium-implanted thin films have a broad band in the range 300–500cm~1 where the vibrational and rotational modes of endohedral Li are predicted.65 A new approach using a radio frequency furnace to evaporate carbon and barium has been used to prepare endohedral barium fullerenes, the products range from Ba@C 74 to Ba@C 136 .66 A detailed study of the reaction conditions required for the synthesis and separation of La@C 82 has been made.67 A number of lanthanide elements have been studied in the formation of endohedral metallofullerenes and some of the endohedrals identified include La@C 74 and M@Cn (M\Eu, Tm or Yb and n\74, 82, 84, 88, 90, 92 or 94).68 The first encapsulation of a radionuclide, 99Tc, has been achieved and it is suggested that 99Tc@C 60 may be used as a radiopharmaceutical for medical imaging.69 The first Dy endohedral fullerene, Dy@C 82 , prepared using the usual composite graphite rod and metal oxide method was extracted from the soot using dmf and purified by HPLC.70 The metallofullerene Ce@C 82 , where the charge state is close to ]3, is the major endohedral species present in the soot formed from CeO 2 graphite composite rods.71 The two La atoms in La 2 @C 80 are found to circulate inside the cage even at room temperature by 13C and 139La NMR experiments.72 Photoelectron spectra provide evidence that the La valence electrons are not completely delocalised on the fullerene cage in La@C 82 ;73 Gd@C 82 and La@C 80 have also been examined using ultraviolet photoelectron spectroscopy.74 The species Sc 3 @C 82 is found to have two reversible oxidation peaks, two reversible reduction peaks and two shoulders at potentials close to the solvent reduction by square-wave voltammetry, the voltammograms are similar to those of other monometallic endohedral fullerenes, e.g. La@C 82 , but Sc 3 @C 82 transfers more electrons to the cage.75 The fullerene cage provides a locally ordered environment for erbium ions in Er 2 @C 82 which emits near infrared fluorescence, it is proposed that the observed line splittings are dominated by an exchange interaction of the Er3` ions which involves a novel superexchange pathway through the [82]fullerene cage.76 The first electron a¶nity measurements for Gd metallofullerenes have been measured and found to be greater than those of the parent fullerenes.77 Tandem mass spectrometry provides a route to the preparation of endohedral fullerene complexes that contain, in addition to the original noble gas atom, an He atom that is encapsulated during collision.78 The ‘window-type’ transition states that are proposed as a method for incorporation of He into, for example, [60]fullerene are found to be stabilised by the incorporation of a C–X bond (where X\H or Me) from the broken C–C bond thus suggesting that radical impurities may account for the formation of He@C 60 .79 The interaction energies andNMRchemical shifts of noble gases in [60]fullerene have been calculated, for example, 129Xe is predicted to be deshielded by about 60 to 70ppm in Xe@C 60 .80 60 P.R.Birkett4 Chemistry of the fullerenes Organic chemistry Reviews of the organic chemistry of [60]fullerene81 and higher fullerenes82 have been published. Photochemical [2]2] cycloadditions of arylalkenes to [60]fullerene occur by a two-step process which involve the formation of a dipolar or radical intermediate in the rate-determining step.83 Irradiation of [60]fullerene with cyclic 1,3-diones leads to the formation of two fused furanylfullerenes rather than the expected De Mayo cyclooctane-1,3-dione addition product.84 A photochemical step in the thermal rearrangement is responsible for the zero-order behaviour of the conversion of the [6,5] open fulleroid to the closed [6,6]methanofullerene.85 Treatment of [70]fullerene with (2-methoxyethoxy)methyl azide produces three out of a possible six triazoline isomers, the major product being addition at the bond (a,b) of greatest curvature.86 Reaction of the dimer (C 59 N) 2 or C 59 HN with diphenylmethane produces the first azafullerene derivative, C 59 (CH 2 Ph)N.42,87 The first example of a transition-metal catalysed carbenoid reaction with [60]- fullerene has produced the [6,6]methanofullerene in good yield and selectivity.88 A new variation of the cyclopropanation of [60]fullerene with malonic acid, iodine and DBU a§ords the 61-iodo-1,2-methano[60]fullerene-61 carboxylates, protection of both of the carboxylic acid groups accordingly produces the 61-dicarboxylate derivative. 89 An alternative procedure for the formation of methanofullerenes involves reaction of [60]fullerene with a 1: 1 mixture of triphenylphosphine and dimethyl acetylenedicarboxylate, the reaction product is obtained as a stable phosphorous ylid.90 Buta-2,3-dienoates and buta-2-ynoates in the presence of phosphine catalysts react with [60]fullerene producing [3]2] cycloadducts91 and not [2]2] cycloadducts as reported earlier.92 Novel amphiphilic methanofullerenes result from the reaction of [60]fullerene with diazo compounds and the experimental evidence that the [6,5]fullerenoid is the thermodynamically stable product in this case has been presented.93 Similarly the [6,5]fulleroid rather than the expected [6,6]fulleropyrrolidine results from the reaction of [60]fullerene with DL-valine.94 There is continued interest in the synthesis and properties of fullerene diads containing covalently linked electron donors (porphyrin, etc.) and an acceptor ([60]fullerene). For example the synthesis of porphyrin–[60]fullerene hybrids have been reported by two independent groups.95 The intramolecular interaction between the fullerene and porphyrin hybrids are enhanced by complexation with metal cations and a high quantum yield of singlet oxygen is observed.95a In addition, long-lived charge-separated states are found in a molecular triad (Por–C–C 60 ) which consists of a [60]- fulleropyrrolidine, a carotenoid polyene linker (C) and a diarylporphyrin (Por), photochemical electron transfer initially produces Por·`–C–C 60 ·~ which evolves into Por–C·`–C 60 ·~.95b In addition, the Diels–Alder methodology has been employed to produce similar [60]fullerene–phthalocyanine diads, including bis-fullerene cycloadducts; the electrochemical investigation of these systems reveals that the electron acceptor properties of the fullerene moiety have no influence on the properties of the phthalocyanine portion of the molecule.96a [60]Fulleropyrrolidine–ferrocene diads exhibit electron transfer between the reactive moieties which evolves from photoinduced bleaching of the fullerene singlet excited state by the ferrocenyl group.97 The first crystal structure of a [60]fulleropyr- 61 Fullerene chemistryrolidine–porphyrin diad reveals a remarkably close approach of the [60]fullerene to the porphyrin at ca. 2.75Å, the spectra of the fulleride(1[) anions are also reported.98 ‘Fullerenocrown’ compounds where several of the fullerene cage carbon atoms are included in a crown ring have been synthesised utilising bis-azide addition to [60]- fullerene, the resultant compounds are found to complex metal atoms with a concomitant change in their UV/VIS absorption spectroscopy.99 Langmuir–Blodgett films of a crown ether group linked to a methano[60]fullerene moiety by a tether have also been prepared and the metal complexing ability of the films examined.100 The easily accessible fulleromalonic acid, C 61 (CO 2 H) 2 , has also been used to synthesise fullerene derivatives, including a 1-aza-12-crown-4-derivative, with side-chain modifications using standard organic coupling reagents such as N,N@-dicyclohexylcarbodiimide.101 A fulleropyrrolidine derivative has been synthesised and covalently linked to HPLC silica gel and the resultant material has been used to separate calixarenes, cyclodextrins and protected peptides.102 Similar technology has resulted in the incorporation of fullerene derivatives into sol–gel matrices, good optical limiting performances have been observed and the high stability of the sol–gel materials under laser irradiation demonstrated by the damage fluence threshold which is higher than 33 J cm~2.103 Fulleropyrrolidines have also been synthesised incorporating a nitroxide group and the compounds reduced to their biradical anions, one electron spin is localised on the nitroxide group and the second located on the [60]fullerene moiety.104 Such derivatives in the presence of ferrocene show intermolecular electron transfer from the ferrocene to the 2,2,6,6-tetramethylpiperidine 1@-oxyl group.105 Two new fulleropyrrolidines, one amphiphilic, the other hydrophobic, have been synthesised and the former forms a stable ‘true’ monolayer in contrast to the latter.106 Other fulleropyrrolidines are also found to form true monolayers and a weak second harmonic generation has been observed.107 In addition, electrodes fabricated from SnO 2 and a Langmuir–Blodgett film of a fulleropyrrolidine derivative have been found to produce a photocurrent.108 The incorporation of a covalently attached positively charged group into fulleropyrrolidines has been shown to enhance both the water solubility and the rate of reduction of the [60]fullerene core.109 The synthesis of covalently linked [60]fullerene derivatives containing ttf groups has been reported using either fulleropyrrolidine,110 or Diels–Alder methodologies.111 Other [60]fullerene-based electron donor–acceptor systems include fulleropyrrolidines with tcnq and dicyanoquinodiimine addends, the first reduction potential for these derivatives is shifted to less negative values when compared with [60]- fullerene.112 Similarly Diels–Alder cycloadditions under both thermal and microwave conditions have been used to produce a variety of cycloadducts and their properties investigated.113 [60]Fullerene is regenerated from isoxazolines in good yield on treatment with Mo(CO) 6 or diisobutyl aluminium hydride.114 The ring-opening of a isoxazoline [60]fullerene derivative has been achieved for the first time using triethylamine in toluene producing 1-cyano-2-hydroxydihydrofullerene. The characterisation of this compound was di¶cult because of its low solubility and therefore the valeric acid ester was synthesised and characterised.115 Control of the regio- and stereo-chemistry of polycycloaddition to [60]fullerene is of growing interest with new strategies being developed to overcome the problems of obtaining mixtures of isomers.The first direct synthesis of bis(imino[60]fullerene) adducts has been achieved by reaction of [60]fullerene with a bis-azide116a and the 62 P.R. BirkettFig. 3 The structure of the first [60]fullerene containing [2]catenane 1 (Reproduced by permission from Angew.Chem., Int. Ed. Engl., 1997, 36, 1448.) electrochemistry of similar singly and doubly bridged imino[60]fullerenes has also been reported.116b The self-assembly of the first [60]fullerene containing [2]catenane 1 (Fig. 3) has been achieved using a regiospecific bis-functionalised [60]fullerene derivative containing a bis(p-phenylene)-34-crown-10 and cyclobis(paraquat-p-phenylene). 117 A detailed study of the selective bis-functionalisation of [60]fullerene with an oligomethylene tether, (CH 2 )n, using bis-a,a@-dibromo-o-xylene groups has been published. 118 A strategy using computational methods for the design of regiospecific synthesis of fullerene derivatives has been developed to find the bond most likely to be approached by a second reactive group as the linking chain moves through its possible conformations after reaction of a first group with [60]fullerene.119 The synthesis of an equatorial tetrakis-adduct by orthogonal transposition was achieved by first synthesising the bis-antipodal anthracene adduct followed by reaction under Bingel conditions to give the hexakis-adduct in extremely good yield (95%), the anthracene units can then be selectively removed producing the tetrakis-adduct.120 The same tetrakis-adduct has also been synthesised using the alternative approach of tetherdirected remote functionalisation,121b bis- through to tetrakis-adducts are reported, selective removal of the tether-reactive group and a good correlation between optical gap, LUMO energy, reduction potential and chemical reactivity was found in a comprehensive study of the properties of the molecules synthesised.121 Using this methodology a mixed [60]- and [70]-fullerene hybrid which consists of a [70]fullerene bearing two [60]fullerene groups has been synthesised for the first time and the synthesis of a new bis-methano[60]fullerene was achieved with regio- and stereoselectivity. 122 Other new previously unobtainable addition patterns have also been achieved.121–123 The method has been extended further and a large number of [60]- fullerene derivatives prepared by macrocylisation of bis-malonates containing o-, m- or p-xylene tethers which have been used as the initiator cores for the construction of fullerene dendrimers.123 Fullerene dendrimers have also been constructed which have 63 Fullerene chemistryan octahedral addition pattern, and have a branching multiplicity of 12, the highest known to date.124 The synthesis of hexakis- and octakis-adducts of [60]fullerene result from the reaction of [60]fullerene pentakis-adducts with diazomethane.125 Separation of [60]fullerene derivatives with an inherent chiral addition pattern has been achieved using a chiral Whelk-O1 column and CD spectra of the enantiomers recorded.126 A detailed configuration representation for the description and nomenclature of chiral fullerenes and derivatives with chiral addition patterns has been published.127 In addition, 3He NMR spectroscopy,128a transient EPR spectroscopy128b,c and the photophysical properties of the multiple adducts of [60]fullerene have been published. 128d The first pure multiple adducts of a mixture of C 2V and D 3 [78]fullerene using cyclopropanation yielded two C 1 -symmetrical bis-adducts and at least eight tris-adducts129 Heating of solid C 120 O at 440 °C in an inert atmosphere produced small quantities ofC 120 O 2 which were separated from the resultant mixture of oxides and [60]fullerene by a two-stage HPLC technique, the compound has C 2V symmetry with two [60]- fullerene cages being bis-linked by adjacent furanoid ring and thus have a connecting four-membered ring.130 Semiempirical models confirm the stability of bridged dimer structures in this and other derivatives.131 Methyltrioxorhenium,CH 3 ReO 3 , catalyses the reaction of [60]fullerene with hydrogen peroxide producing the fullerene epoxide, C 60 O, and other [60]fullerene higher oxides.132 Two isomers, 1,2-epoxy[70]fullerene and 5,6-epoxy[70]fullerene of the analagous [70]fullerene epoxide, C 70 O, have been isolated from fullerene soot extract using HPLC, both are [5,6]-addition products.133 Oxidation of [60]fullerene with ozone produces C 60 On (n\1–5), two isomers of the bis-adducts and three of the tris-adducts were identified.134 High temperature oxidation of [60]fullerene with oxygen atoms was studied behind reflected shock waves by time-dependent atomic and molecular resonance absorption spectroscopy and a rate coe¶cient of 3.0]10~15 calculated for the rate of formation of carbon monoxide under such conditions.135 The optical and photodesorption spectra of fluorinated [60]fullerene derivatives suggest that atomic or molecular relaxation after electronic excitation of the C–F bonds results in the decomposition of the [60]fullerene cage.136 Photoluminescence studies of C 60 Fx (xO48) show that the absorption is maximised around 6.4 eV and broad luminescence bands appear at around 2.4 and 3.3 eV.137 The electron a¶nities of monofluorinated [60]- and [70]-fullerenes in the gas phase have been estimated to be P283 and P288 kJ mol~1 respectively.138 Reaction of [70]fullerene with liquid Br 2 with or without a solvent produces C 70 Br 14 .139 Addition of a variety of aromatic compounds (RX) to C 60 Cl 6 under Friedel–Crafts conditions results in the formation of C 60 (RX) 5 Cl derivatives which can be reduced to C 60 (RX) 5 H.140 Similarly a symmetrical 1,4-addended [60]fullerene derivative, C 60 Ph 2 , and an unsymmetrical derivative, C 60 Ph 4 , have been characterised as minor products of the reaction of C 60 Cl 6 with benzene.141 Exposure of C 60 Ph 5 H and C 60 Ph 5 Cl to air at room temperature results in their oxidation to an unsymmetrical benzo[b]furanyl[60]fullerene which has an additional oxygen atom located in the pentagon surrounded by phenyl groups.142 Addition of phenyl radicals to [60]fullerene has been achieved using both electrochemical and photochemical reaction techniques and products with up to 10 phenyl groups added have been identified.143 Addition of benzene to [60]fullerene using a catalyst based upon AlCl 3 and CuCl 2 a§ords C 60 Ph 19 H 19 , which when 64 P.R. Birkettheated to 400 °C eliminates hydrogen to give C 60 Ph 19 .144 Addition of potassium fluorenide to [60]fullerene results in the formation of the first tetrakis-adduct which has a fulvene-type n system, the crystal structure of the tetrakis-adduct and the aromatic cyclopentadienide anion of the pentakis(9-fluorenyl)[60]fullerene have also been reported.145 Theoretical and experimental evidence indicates the presence of a strong endohedral homoconjugation in C 60 PhSH, n–n orbital interactions are also evidenced inside the [60]fullerene cage in the analogous pentakis(phenyl)[60] fullerene anion.146 The base catalysed rearrangement of 1-tert-butyl-1,4-dihydro[60] fullerene to the 1,2-isomer was found to be a second-order process by NMR experiments147 and has an activation energy of 56.1 kJ mol~1.Photolysis of [60]fullerene with cyclic amino acids produces 1,2-dihydro[60]fullerenes rather than fulleropyrrolidines by a decarboxylation process.148 Reduction of [60]- and [70]-fullerene with, for example, Zn(Cu) leads to the formation of a surprisingly small number of isomers of C 60 H 2 , C 60 H 4 and C 60 H 6 and only three isomers of C 70 H 10 .149 Similarly reduction of He@C 60 with anhydrous hydrazine produces a mixture of isomers of He@C 60 Hx.150 The HPLC isolated derivatives were examined using 3He NMR with, for example, six isomers of He@C 60 H 4 found.Only two signals were observed in the 3He NMR spectrum of 3He@C 60 H 36 , the major signal corresponding to the D 3${ symmetrical structure.151 Photoinduced electron transfer from 10-methyl-9-,10-dihydroacridine to the triplet excited state of [60]fullerene in the presence of trifluoroacetic acid can also be used to synthesise 1,2-dihydro[60]fullerene, C 60 H 2 .152 Proton transfer from 9,10-dihydroanthracene results in the formation of C 60 H 36 as the main reaction product and the product is suggested to be the T-symmetric derivative.153 Hydrogen absorbing metal alloys have also been used to hydrogenate [60]fullerene in the solid state with an average content of 24–26 hydrogens per fullerene molecule found in the resultant products.154 A 750MHz NMR examination of the proton spectra of C 60 H 2 and C 60 H 4 reveals evidence for anisotropic dipole–dipole couplings.155 Semiempirical molecular orbital (MNDO) calculations on C 60 X 36 and C 70 X 36 (X\H or F) show that the driving force for reaction appears to be the relief of steric strain in the fullerene cage rather than electronic considerations.156 The spectroscopic and photophysical properties of C 60 H 18 are found to be similar to those of [60]fullerene while more highly hydrogenated [60]fullerenes such as C 60 H 36 become more like those of aromatic systems such as benzene.157 A polyfullerenol has been found to suppress the levels of the microsomal enzymes in vivo and decrease the activities of P450-dependent monooxygenase and mitochondrial oxidative phosphorylation in vitro.158 The same material produced a gradual increase in the airway constriction with time in guinea-pigs and oxygen radicals were found to play an important role in this exsanguination-induced bronchoconstriction.159 The LD 50 value of a water-soluble polyarylsulfonated [60]fullerene derivative is 600mgkg~1.160 Water-soluble polyethylene modified [60]fullerene accumulated at the site of tumours during testing and after light irradiation the volume of the tumour was significantly reduced.161 The species C 61 (CO 2 H) 2 inhibits the endothelium nitric oxide-dependent relaxation induced by acetylcholine, but does not a§ect the agonistinduced contractile response of smooth muscle.162 The same authors report that production e¶ciency of singlet oxygen of several [60]fullerene derivatives decreases with an increase in the number of addends, adjacent addends causing a greater 65 Fullerene chemistrydecrease than more remote addends; thus the photodynamic activity of polyaddened [60]fullerene is reduced.163 Polymers Novel copolymers of average molecular weight 5–6]104 have been synthesised by reaction of bis(methanofullerenes) with isophthalic acid and 4,4@-diaminodiphenyl ether.164 [60]Fullerene has also been grafted onto ethylene–propylene copolymers using radical addition reactions165 and a living butyl terminated polyacrylonitrile has been reacted with [60]fullerene to produce a highly soluble star-like polymer. 166 Novel polymers have also been synthesised by first preparing azido containing polymers which are then reacted with [60]fullerene and as the fullerene content of the polymer increases the glass transition temperature of the polymer rises.167 Photochemical addition of furan derivatives to [60]fullerene produces highly cross-linked polymers,168 whilst distinct glass transitions are not observed in [60]fullerene containing polyimides.169 Highly water-soluble polymers have been prepared by the photochemical reaction of secondary amino groups in preformed aminopolymers with [60]fullerene.170 Well defined star-shaped polymers have also been prepared by grafting [60]fullerene to living anionic, polystyrene and polyisoprene, the maximum number of grafts per fullerene molecule is six.171 An alternative approach to fullerene polymer synthesis involves initial preparation of C 60 anions and the use of these derivatives as initiators for anionic polymerisation, in this study only C 60 6~ was able to polymerise methyl methacrylate.172 Polystyryllithium was also added to [60]fullerene with six carbanions required to be attached to the fullerene core in order for polymerisation of styrene to occur.172 [60]Fullerene retards the free radical polymerisation of methyl methacrylate although the e§ect is small and multiple radical additions to each [60]fullerene unit occurs producing star-like polymers.173 [60]Fullerene derivatives with a first reduction potential higher than that of [60]- fullerene itself, produce a new photoluminescence signal in the near IR which results from radiative electron–hole recombination between the fullerene excited state and the polymer ground state in mixed films with conjugated polymers.174 As a result of the e¶cient photoinduced intermolecular charge transfer, the photoinduced absorption and reflectance spectra of composite films of methanofullerenes and poly(3-octyl thiophene) are significantly enhanced.175 The spectral signature of the [60]-fullerene anion at 1.15 eV has been observed by infrared photoexcitation spectroscopy.176 A study of the mechanism of the enhancement of photoconductivity in fullerene photoconducting polymers has been published and includes a new theoretical model combining both Onsager and Marcus theory.177 The optical limiting properties of [60]- fullerene–polystyrene systems has been attributed to the non-linear absorptions in the pendant [60]fullerene–styrene polymer and are comparable to those of [60]- fullerene.178 The charge-transfer range was estimated to be 80Å and results from quantum delocalisation of the photoexcitations in [60]fullerene conducting polymer composites.179 Doping of conducting (disilanyleneoligothienylene) polymers with [60]fullerene was found to enhance the photoconductivity quantum e¶ciency e§ectivity to 85%.180 Fabrication of polymer grid triodes incorporating [60]fullerene as a semiconducting medium have been reported with performance advantages over pure polymer devices which, for example, include operating voltages of less than 5V.181 66 P.R.BirkettHighly e¶cient photoconducting devices consisting of [60]fullerene and polythiophene derivatives have also been prepared.182 Organometallic chemistry Reviews of the organometallic chemistry of fullerenes have been published.183 Dendrimer containing irdium compounds, trans-Ir(CO)Cl(PPh 2 R1) 2 and trans- Ir(CO)Cl(PPh 2 R2) 2 where R1\3,5-bis(benzyloxy)benzyl and R2\3,5-bisM(3,5- bis(benzyloxy)oxyNbenzyl bind reversibly to [60]fullerene, crystal structures of the monoaddition products have been reported and thermodynamic data obtained by line-width analysis of the 31P-M1HN NMR spectra.184 Air-stable and organic solvent soluble tungsten and molybdenum g2-complexes of [60]fullerene, [MM(CO) 2 (phen) 2 (L)NC 60 ] (M\Wor Mo, L\dibutyl maleate), have been prepared; the metal co-ordination is distorted octahedral with the two CO groups and phen in the equatorial plane.185 Similar g2-complexes of [60]fullerene containing 1,2- bis(diphenylphosphino)benzene ligands have also been synthesised.186 Platinum(0)–[60]fullerene complexes, [Pt(g2-C 60 )(L–L)], containing diphosphine complexes have been produced by reaction of a preformed PtC 60 complex with bidentate phosphines L–L (dppe or dppp) or by adding an equimolar amount of [Pt(cod) 2 ] to [60]fullerene followed by the corresponding diphosphine.187 In addition [Pt(PCy 3 ) 2 (g2-C 60 )] has been synthesised in quantitative yield.188 Variable-temperature NMR studies have shown that organotransition-metal [60]fullerene complexes, [M(NO)(PPh 3 ) 2 (g2-C 60 )] (M\Co or Rh), [Ru(NO)(PPh 3 ) 2 (g2-C 60 )H] and [Rh(CO)(PPh 3 ) 2 (g2-C 60 )H] undergo rotation about the metal–fullerene bond axis and migration of the metal fragment about the surface of the [60]fullerene results in new complexes with di§ering symmetry and concomitantly significantly di§erent NMR spectra.189 Dicobalt and dinickel complexes of trimethylsilylethynyl-1,2- dihydro[60]fullerene have been prepared, in these cases the metal preferentially coordinates to the ethynyl bond rather than [60]-fullerene.190 The catalytic activity of palladium supported on [60]fullerene has been found to have comparable or better activity than conventional Pd on charcoal catalysts.191 Reaction of [70]fullerene with [Ru 3 (CO) 12 ] provides the first hexahapto-[70]fullerene complex, [Ru 3 (CO) 9 (k3- g2:g2:g2-C 70 )] 2 (Fig. 4). The Ru 3 cluster is co-ordinated to one of the six-membered ring types at the pole of the [70]fullerene and addition of a second Ru 3 cluster to 2 produces a mixture of isomers one of which, the C 2 symmetrical derivative 3, has been characterised using single-crystal X-ray di§raction techniques.192 Inclusion and charge-transfer complexes Out of twenty-eight calix(n)arenes examined only three, homooxacalix[3]arene, calix[5]arene and calix[6]arene, each of which possesses a cone formation and a benzene ring inclination, interact with [60]fullerene in solution.193 The crystal structure reveals a layered structure of [60]fullerene with p-iodocalix[4]arene benzyl ether even though there are no appreciably strong intermolecular interactions present.194 Two bis mixed p-methyl/iodio calix[5]arene molecules form a cavity in which one [60]fullerene molecule resides in the solid state, the structure of the complex in solution was disclosed by the ring current method based on X-ray crystallographic analysis.195 In contrast, the 1: 1 complexes are observed in the analagous all p-methyl substituted calix[5]arene: [60]fullerene complex.196 Complexation of [60]fullerene 67 Fullerene chemistryFig. 4 A perspective view of compounds 2 and 3, showing part of the atom labelling scheme (Reproduced by permission from Chem. Commun., 1997, 1125.) 68 P.R. Birkettwith p-benzylcalix[5]arene produces a partial molar volume change of ]195cm3 mol~1 which is consistent with displacement of two toluene molecules from the cavity of the calixarene.197 A new mesoporous silica (MPSiO 2 ) has been loaded with [60]fullerene and displays an interfullerene resonant transition at ca. 450nm in the reflectance spectrum indicating that the [60]fullerene molecules undergo aggregation within the silica pores.198 When [60]fullerene is introduced into the Fe3` exchanged zeolite Y an intense EPR signal due to the formation of the radical cation, C 60 ·`, is observed.199 Similarly [60]fullerene has been adsorped into Na zeolite Y by a vapour phase method.200 High-resolution electron microscopy of the complex reveals that the [60]fullerene molecules are dispersed throughout the zeolite molecules and that in some regions there are preferential spatial arrangement of [60]fullerene. When [60]fullerene is incorporated into aqueous micelles of reduced triton-X100 in the presence of an electron donor the radical anion, C 60 ·~, is formed upon photolysis.201 Intercalation of functionalised dendritic methano[60]fullerenes between two monolayers of a lipid bilayer results in the formation of rod-like structures that exhibit long-range ordering.202 A series of crystal structures of [60]fullerene with electron donors such as 9,9@-transbis( telluraxanthene), C 26 H 18 Te 2 have been reported203 with weak charge transfer observed by XPS and IR spectroscopy in some examples.203a [60]Fullerene has been coated with a layer of weakly bound sulfur or phosphorus molecules in the gas phase.204 Thermal desorption spectroscopy, thermal analysis and di§use reflectance IR spectroscopy reveal thatO 2 is readily intercalated into pristine samples of sublimed [60]fullerene.205 In an independent study dielectric spectroscopy shows that the intercalation of O 2 from air into [60]fullerene results in a weak charge transfer which creates large dipole moments and these are coupled to the applied a.c.electric field via a di§usion controlled relaxation mechanism.206 Similarly CO can be intercalated into [60]fullerene in a 1: 1 ratio, the IR spectra indicate a transition from nearly free motion of CO at room temperature to hindered motion at low temperature with only tunnelling between symmetry equivalent orientations remaining.207 Metal fullerides and polymeric fullerene phases Reviews of the synthesis and properties of metal fullerides208 and a special edition of Appl.Phys. A dedicated to polymeric fullerenes209 has been published. Pure KC 60 is obtained by reaction of [60]fullerene with potassium carbonate despite the presence of oxygen released during heat treatment of the mixture.210 The single crystal structure of a novel alkali-metal salt containing alternating layers of C 60 2~ anions and [KL] 2 ` cations (L\cryptand 222) has been obtained, the fulleride anions form distorted hexagonal layers parallel to the ab plane separated by the layers of cations.211 Reaction of Na 2 C 60 with ammonia at low temperature results in rhombohedral packing of (ND 3 ) 8 Na 2 C 60 which arises from the rearrangement of the fcc structure of the starting material, the interlayer fulleride distance of 10.24Å is maintained and the ABC stacking sequence is retained, whilst the intralayer interfulleride distance is increased to 12.22Å.212 The structure of (NH 3 )xK 3 C 60 (0\x\1) is fcc and is superconducting with the onset temperature of T# 8.5 K.213 Synthesis of rubidium fullerides can be performed with alkylamines as solvent, the amine may be removed from the final product by heating.214 It is proposed that initially a fullerene–amine adduct forms, charge transfer then occurs between the [60]fullerene adduct and Rb 69 Fullerene chemistryFig. 5 Static 13C NMR spectra of RbC 60 at indicated temperatures. The narrow line at d 143 is due to residual [60]fullerene.Bottom: simulation of an sp2 and sp3 tensor pattern with an intensity ratio of 59: 1 (Reproduced by permission from Phys. Rev. B, 1997, 55, 124.) metal and the metal adduct complex then undergoes thermal decomposition to yield Rb 3 C 60 . The air-sensitive C 60 4~ anion precipitates from solution after reaction of [60]fullerene with sodium in thf in the presence of cryptand 222.215 A novel fulleride compound, NaCoC 60 , in which the Co is covalently attached to [60]fullerene has been prepared by an electron transfer reaction of [60]fullerene with Na[Co(CO) 4 ].216 The species NaxHyC 60 (x\3.6, yB4) which is prepared with NaH has an fcc structure with o§-centered Na` ions in the octahedral and tetrahedral interstices.217 The variation of the superconducting transition temperature T# with hydrostatic pressure was measured for Rb 3 C 60 and found to be almost linear.218 The missing stoichiometric phase Na 4 C 60 has been prepared and found to be body-centred monoclinic with polymer planes of [60]fulleride, each molecule forms four single bonds within the plane, the sodium ions are situated at two symmetrically inequivalent positions in the structure at the centres of distorted tetrahedra.219 Alkali-metal fulleride samples, KxC 60 and RbxC 60 , with stoichiometries close to four have a charge per lattice site that is closer to an integer than any other fulleride and the [60]fullerene molecules are found to be disordered between two possible orientations within the body-centred 70 P.R.Birketttetragonal lattice.220 At ambient pressure and low temperatures the ground state of Na 2 RbC 60 is a non-superconducting orthorhombic phase with a short interball distance of 9.38Å consistent with covalently bonded C 60 3~.221 A new phase-transition to the orthorhombic phase on cooling of Na 2 RbC 60 has been observed for the first time using variable-temperature solid-state NMR spectroscopy.222 An X-ray structural analysis of the dimer phase of AC 60 (A\K or Rb) has been reported.223 In addition, an IR study of RbC 60 224 and an NMR study of the polymerised phase of CsC 60 225 have been published.High-resolution 13C NMR spectroscopy proves the existance of sp3 carbon atoms in RbC 60 which are assigned to the dimer bonds in the quenched phase (Fig. 5).226 An antiferromagnetic resonance has been observed in the powders of conducting alkali-metal fulleride linear polymers, RbC 60 and CsC 60 , which provides proof for an antiferromagnetically ordered ground state and shows that these systems are not spin glasses.227 The origin of the splitting of the 87Rb NMR signal of Rb 3 C 60 has been suggested to be due to vacancies in the crystal lattice, however an NMRstudy of Rb 2 CsC 60 provides evidence that vacancies, if present, are unrelated to theNMRsplitting.228 Calculations predict that theLUMO band structure in the family A 3 C 60 (A\K, Rb or Cs) splits into three similar sub-bands showing an overall occupied bandwidth of 1 eV and a steep decrease of the density of states at the Fermi level when the band population deviates from half- filling.229 An EELS study provides evidence for a Mott–Hubbard ground state in A 4 C 60 (A\Na, K, Rb or Cs) with a Jahn–Teller distortion of the fullerene molecules. 230 EELS also reveals that the crystal symmetry remains fcc through the entire intercalation range in NaxC 60 (4\x\10) and that on intercalation to higher levels the charge transfer from sodium to [60]fullerene becomes incomplete.231 Three distinct phases are found in barium-doped [60]fullerene using valence band photoemission and X-ray absorption spectroscopy and the experimental observations indicate that fulleride formation leads to the occupation of hybrid bands on both sides of the Fermi level.232 Inelastic neutron scattering experiments provide evidence for the formation of charged fullerene dimers in RbC 70 , the concentration of dimers are found to decrease above 400K but there is no transition observed to a pure rotator phase even at temperatures above 500 K.233 A frequency shift of only the tangential modes is observed in the Raman spectroscopy of TDAE–C 60 single crystals while in the IR measurements the radial modes are also observed to shift, the e§ect being attributed to Raman resonance with di§erent relaxed states of C 60 ~.234 Squid magnetometry of TDAE–C 60 after slow cooling shows evidence for a superconducting phase below T# \17.4K which co-exists with the known magnetic phase.235 The weak ferromagnetism of TDAE–C 60 is proposed to occur by inhomogeneous distribution of the spin density of the charge on TDAEwhich leads to the TDAE mediated superexchange producing a ferromagnetic coupling between C 60 ~ ions in di§erent chains.236 Single crystals of [60]fullerene can be polymerised under relatively modest pressure and temperature conditions, the resultant material displays long-range order, has an orthorhombic structure and short distances along the polymeric chains of [60]- fullerene of 9.14Å, consistent with the presence of covalent bonding.237 The IR spectra of pressure-induced rhombohedral, tetragonal and orthohombic [60]fullerene polymers have been recorded and the vibrational spectra obtained from a first-principles molecular dynamics calculation for [60]fullerene, [60]fullerene dimer and an infinite 71 Fullerene chemistryFig. 6 Schematic illustration for the immobilisation of DNA on the cationic selfassembled monolayer containing [60]fullerene on gold (Reproduced by permission from Chem. Commun., 1997, 1507.) chain of polymerised C 60 .238 Similarly, spectroscopic studies confirm that the rhombohedral and tetragonal phases are present in pressure- and temperature-polymerised [60]fullerene.239 An orthorhombic phase which belongs to the Pnnm space group has been identified which is di§erent to the previously identified high-pressure orthorhombic phase.240 It has also been found that a rhombohedral structure fits the experimental data at least as well as the orthorhombic one does for the structural data of pressure-polymerised [60]fullerene.241 A crystal orbital approach has been used to calculate the band structure and solid-state electronic properties of three polymerised [60]fullerene phases.242 Fullerene films and scanning tunnelling microscopy studies The site-specific photocleavage of immobilised DNA on a cationic self-assembled monolayer on a gold substrate is achieved by covalent incorporation of [60]fullerene into the monolayer (Fig. 6).243 Sol–gel processing using phenyltriethoxysilane can be used to incorporate [60]fullerene into silicon oxide thin films.244 Irreversible oxidation of [60]fullerene is observed when [60]fullerene is absorbed onto TiO 2 .245 Mass selected [60]fullerene molecules were accelerated to di§erent kinetic energies and collided with the (111) surface of a gold single crystal or highly orientated pyrolytic graphite and found to deform to planar structures which were not dissociated.246 The growth of [60]fullerene films on GaAs (100)247 and GaAs (001) As-rich 2]4248 substrates has been studied using STM.In the latter case the [60]fullerene takes its (110) crystalline axis which is highly strained with the arrangement stable up to 10 monolayers thick and has a lattice expansion of about 13%. The conditions required for manipulation of a single [60]fullerene molecule on a surface with STM have been 72 P.R.Birkettmodelled using molecular mechanics calculations249 and a study of the concepts of experimental requirements for individual positioning, patterning and exploring the functionality of [60]fullerene molecules using STMhas been published.250 Manganese clusters deposited on [60]fullerene-terminated Si (111) 7]7 may be removed during scanning at negative sample bias.251 A procedure has been developed for the atomic scale alignment with respect to macroscopic objects and these procedures have been used to investigate the interaction of Ag with a patterned [60]fullerene layer deposited on Si (111) 7]7.252 Silicon carbide films have been grown by annealing [60]fullerene deposited on Si at 900 °C for 300 min and this method provides a method for patterning SiC structures on Si with submicron resolution.253 Photoemission studies of [60]fullerene monolayers adsorbed on Cs precovered Au (110) display discrete molecular oxidation states of approximately [3, [4 and [6 which were determined by comparison of monolayer electronic structure and vibrational mode frequencies with those of the bulk fulleride salts.254 High-resolution vibrational spectroscopy has been used to demonstrate adsorbate–substrate dynamic charge transfer by doping [60]fullerene adsorbed on Ag (111) with potassium.255 Only the [60]fullerene molecules in contact with the substrate layer display significant changes in electronic structure.256 The band gap in a monolayer of [60]fullerene on a Ag surface is reduced considerably and it is argued that this is due to the influence of image charges in the metal substrate suggesting that the physical properties of correlated insulators and semiconductors will be modified if prepared in ultra-thin form on metal substrates.257 The photoluminescence spectra of [60]fullerene thin films on Si, GaSe, GaAs and Au substrates have been reported258 while the electronic structure of [60]fullerene films grown on Ag (110) has been investigated using high-resolution synchotron radiation.259 High-resolution EELS indicates the formation of covalent bonds between [60]fullerene molecules in sub-monolayer films and the Si (111) 7]7 substrate, after completion of the [60]fullerene monolayer there is evidence for the breaking of these bonds and the formation of a new double-domain [60]fullerene structure.260 Carbon nanotubes and related materials A number of reviews of carbon nanotubes have been published.261 Gram quantities of well defined single-walled nanotubes (SWNT) in the form of highly crystalline bundles have been produced by using an electric arc-discharge technique which incorporates the use of a metal catalyst.262 Aligned-nanotube bundles have been generated by pyrolysis of 2-amino-4,6-dichloro-1,3,5-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching.263 Perfect carbon tori have been observed amongst SWNT264 and these materials have been predicted to exhibit interesting transport properties.265 Samples consisting entirely of graphitic cones which are formed during high-temperature pyrolysis of hydrocarbons have total disinclinations that are multiples of 60°.266 A number of methods for the production of nanotubes and related materials have now been reported including catalytic decomposition of hydrocarbons over a metal or metallocene catalyst,267 electric arc-discharge268 and laser evaporation.269 Pyrolysis of hexamethyldisilazane-derived silicon carbonitride powders in a graphite furnace at 1400 °C produces nanotubes in good yield.270 The explosive decomposition of 1,2: 5,6: 11,12: 15,16-tetrabenzo- 3,7,9,13,17,19-hexahydro[20]annulene produces both onion and tube-like closed car- 73 Fullerene chemistrybon particles.271 Carbon onions have been synthesised by either the high-fluence implantation in silver substrates heated at 500 °C272 or by the electron irradiation of single- and multi-walled nanotubes, which results in the continuous loss of carbon atoms as a result of sputtering and induces a surface tension which can be identified as the source of the formation of concentric-shell carbon onions.273 Nanoparticles and tubes containing B and N have also been synthesised using the standard techniques.274 Arcing of a hafnium diboride rod with graphite produces tubes which have a sandwich structure with carbon layers both in the centre and in the periphery separated by a few layers of BN.274a Gallium nitride nanorods have been prepared by reaction of Ga 2 O with NH 3 in the presence of carbon nanotubes, it is thought that the nanotubes act as a template for the formation of the gallium nitride rods.275 Similarly, hollow nanotubes of zirconia have been prepared by coating carbon nanotubes with zirconium n-propoxide, followed by calcination and then heat treatment to oxidatively remove the carbon tubes.276 The method has also been extended to include the synthesis of SiO 2 , Al 2 O 3 , V 2 O 5 and MoO 3 hollow tubes.277 Silicon nitride nanoscale rods have also been prepared in the presence of carbon nanotubes with Si and SiO 2 in a nitrogen atmosphere.278 The template technique has also been used to prepare Pt-filled uniform carbon nanotubes in which the metal is present as either nanorods or nanoparticles.279 Anode activation allows the growth of chromium containing metallic fibres within carbon nanotubes.280 Crystals of rare earth carbides are encapsulated within carbon cages and tubes during their arcdischarge formation.281 An alternative approach to the encapsulation of materials involves opening of the tubes282 and then introduction of a new material via reaction with metal complexes.283 High hydrogen uptake has been observed in SWNT making these materials candidates for hydrogen storage material fuel-cells.284 Argon has also been trapped in carbon nanotubes by hot isostatic pressing, the Ar pressure within the tubes was found to be about 60MPa and was retained for many months.285 A purification procedure which separates carbon nanospheres, metal particles, polyaromatic carbons and SWNT by the suspension of the crude material in an aqueous solution using a cationic surfactant and subsequent trapping of theSWNTon a membrane filter has been developed.286 An alternative method incorporates a hydrothermal treatment, along with extraction of fullerenes and oxidation and dissolution of metal particles.287 High-resolution electron microscopy of non-graphitising carbon after heating reveals the presence of closed carbon nanoparticles which are apparently fullerene-like in structure.288 It is possible to double the diameter ofSWNT by annealing at 1400 or 1500 °C, up to 60% of the tubes coalesce under these conditions289 and the length of the tubes can be controlled by applying a voltage pulse to the tip of a STM which results in a local cut of the tube.290 Raman scattering,291 electron di§raction,292 EPR and microwave resistivity293 of SWNT have been reported. First-principle molecular dynamics simulations show that the end geometry of the tubes is highly reactive and readily accommodates incoming carbon fragments suggesting that the model of growth by chemisorption from the gas phase may be correct.294 Electrical transport measurements on individual SWNT reveal that electrical conduction appears to occur through well separated discrete electron states that are quantum-mechanically coherent over a long distance.295 The metallic resistivity of crystalline ropes of SWNT has been measured and found to decrease as the pressure 74 P.R.BirkettFig. 7 Resistivity vs. temperature for SWNT rope materials: as-grown and lightly pressed mat of SWNT (four-point, unorientated) and single-rope (two-point, scaled to four-point measurement at ambient T).Solid curves are guides to the eye (Reproduced by permission from Phys. Rev. B, 1997, 55, 4921.) applied to the SWNT samples is increased, the highest pressure applied signals the point at which mechanical damage to the SWNT in the mat overtakes the improvement in inter-mat contacts (Fig. 7).296 Doping of SWNT by vapour-phase reactions with Br 2 and K decreases the resistivity by up to a factor of 30 and enlarges the region where the temperature coe¶cient of resistance is positive.297 Raman scattering studies of doped SWNT provide convincing evidence for charge-transfer in K, Rb and Br 2 doped samples.298 Calculations indicate that bond rotation defects close the gap in large-gap nanotubes, open the gap in small-gap nanotubes, and increase the density of states in the metallic nanotubes.299 The predominance of hole transport in the electric conduction of thin films of carbon nanotubes has been shown by Hall coe¶cient and magnetoresistance measurements.300 Magnetotransport behaviour in bundles of intercalated carbon nanotubes shows two types of behaviour, universal conductance fluctuations for T\10K and an underlying positive magnetoconductance to very high magnetic fields for T\100 K.301 Carbon nanotubes have been discussed in terms of their use as materials for next generation electronic devices.302 Some interesting materials properties have already been discovered and devices using nanotubes constructed, for example, a field electron emitter has been constructed from a hollow open-ended carbon nanotube.303 An independent study reports that aligned carbon nanotube films are good field emitters producing large currents at low electric fields and it has been suggested that the observed electron emission is related to the special electronic structure of the nanotube tips.304 A low-energy electron point source microscope has been used to mount an individual carbon nanotube onto aWtip and the electrons generated from subsequent experiments used to generate holograms.305 Similarly, nanotube field emitters with carbon nanotube tips sharpened by exposure to a microwave oxygen plasma have 75 Fullerene chemistrybeen fabricated.306 A STM has been used to explore the local electrical characteristics of SWNT and well defined positions located where the transport current changes abruptly from a graphitic-like response to one that is highly non-linear and asymmetrical including near rectification consistent with the existance of localised, on-tube nanodevices.307 High power electrochemical cells have been constructed from electrodes of entangled nanotubes of high purity and narrow diameter and specific capacitances of 102 and 49Fg~1 were observed at 1 and 100 Hz.308 Carbon nanotubes dispersed in ethanol are aligned by an electric field and display anisotropic behaviour, transmission experiments show rotation of the linear polarisation of an incident laser beam.309 Platinated and iodinated oligonucleotides have been immobilised on carbon nanotubes and such materials may find use in the study of molecular recognition processes.310 A molecular dynamics simulation has been used to investigate the design and properties of theoretical gears constructed from novel nanotubes prepared via chemical modification.311 Nanotubes have been reacted with fluorine and the structure of the nanotubes observed to be modified.312 Multiwalled carbon nanotubes can be bent repeatedly through large angles using the tip of an AFM without undergoing catastrophic failure suggesting that nanotubes are extremely flexible and resilient.313 It has been calculated that the Youngs modulus and the torsion shear modulus of nanotubes are comparable to those of diamond, while the bulk modulus is smaller.314 References 1 R.F.Curl, Rev. 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ISSN:0260-1818    

DOI:10.1039/ic094055

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

6 Carbon, silicon, germanium, tin and lead By D.A. ARMITAGE Department of Chemistry, King’s College, Strand, London WC2R 2LS, UK This reviewcovers the literature for 1997. The synthesis of nanostructures based on the ethynyl substitution of the ethene, cyclobutadiene, and cymantrene (CpMn) residues which extensively use silyl- and stannyl-alkynyl intermediates have been reviewed.1 These could well be used as intermediates in the synthesis of newallotropes of carbon, along with the incorporation of diyne units between arene rings.The intermediates 1 and 2 have been prepared, the synthesis of the former involved the Pd catalysed oxidative coupling of the o-disubstitutedaryl diyne with 1,2-diiodobenzene to give 1 in 31%yield.2 The compound 2 resulted fromthe use of 1,2,4,5-tetraiodobenzene. C C C C C C C C C C C C 1 C C C C C C C C C C C C C C C C C C C C C C C C 2 Coupling Ph 2 (HO)CC–– – CH with indenyl–RuII complexes provides a route to the allenylidene complexes [Ru(––C––C––CPh 2 )(g5-1,2,3-Me 3 C 9 H 4 LL@][BF 4 ] with C–C bonds of 126pmfor Ru–C– –Cand135pmfor C––CPh 2 [LL@\(CO)PMe 3 ].3 Oxidative coupling of Cp*Re(NO)(PPh 3 )C–– – CH using Cu(OAc) 2 gives the ReC 4 Re assembly as orange crystals that can be isolated as the diyne with C–C bond lengths of 120.2 and 139.8pm, corresponding to triple and single bonds.Oxidation using AgPF 6 gives a deep blue dication with a heterocumulene structure (Re`––C––C––C––C––Re`) and C–C bond lengths of 126–130.5pm.4 The trimesitylsilyl cation has been successfully prepared from allyltrimesitylsilane by removal of the exposed allyl group with [Et 3 SiCH 2 CPh 2 ]`, giving a 29Si NMR signal at d 225.5.This signal is static in the presence of aromatic solvents which co-ordinate with the less hindered Et 3 Si`, showing that the o-methyl groups shield the larger solvents e§ectively, although acetonitrile and small amines co-ordinate to give 85SiH2 3 Si TbtLi –78 °C Tbt H Si NBS LiAlH4 Tbt H NBS Si Tbt Br Si Tbt LiBut Scheme 1 Tbt –– 2,4,6-[(Me 3 Si) 2 CH] 3 C 6 H 2 peaks at d 37.0 (CD 3 CN) and d 47.1 (Et 3 N).Calculations support the internal stabilisation of the 2-silanorbornyl cation.5 The first silanaphthalene has been synthesised as colourless crystals, m.p. 151–155 °C, from the base elimination of HX from progressive substitution of the benzosilacyclohexene 3 (Scheme 1).The Tbt substituent at Si is almost orthogonal with the naphthalene plane indicating little conjugation and, while the coupling constants for Si and the ring carbon atoms and planarity at Si support multiple bonding, Si–C bond lengths have as yet to be determined with any significant degree of accuracy.6 Di-tert-butylcyclopropenone reacts with (Me 3 Si) 3 SiLi to give the silatriafulvene 4 which readily adds to 2,3-dimethylbuta-1,3-diene and anthracene as trapping agents.Heating the latter regenerates 4 which isomerises to the silacyclobutadiene which adds Bu5OH to give the isomeric silacyclobutenes 5a and 5b in the ratio 3: 1 (Scheme 2).7 The silylene Tbt(mes)Si: adds to isocyanide to give the first stable silylene–Lewis base complex.The SiCN angle is 163° and the isocyanate–silicon bond of 188.2pm compares closely with typical Si–C single bonds [equation (1)].8 Tbt(mes)Si: + PhNC C NPh Tbt(mes)Si (1) The bis(silacyclopropane) 6 reacts with bis(trimethylsilyl)acetylene to give the bis(silacyclopropene) 7 which isomerises at 120 °C to give the disilabenzvalene 8, m.p. 161–164 °C [equation (2)].It is both water- and air-sensitive and results at room temperature from 7 in the presence of catalytic amounts of AgBF 4 .9 Calculations indicate that the stability of silynes relative to isomeric silylidenes and silavinylidenes depends on electronegative substituents at silicon. Bulky electropositive silyl groups should stabilise linear disilynes.10 The cyclic silylene and germylene :M(Bu5NCH 2 CH 2 NBu5) (M\Si or Ge) react to give the silylgermylene possibly through the germasilene as an intermediate. Dimerisation gives the (Z)-1,2-diaminodisilyldigermene with a long Ge–– Ge bond (245 pm) and subsequent oxidation gives the digermadioxetane.11 The stannaethene 10 results from reaction between hindered diarylstannyleneR 2 Sn: (R\2-Bu5-4,5,6-Me 3 C 6 H) and the cryptodiborylcarbene 9.The structure shows a planar environment at three-co-ordinate tin, and a slight twisting of the Sn––C double bond which is 203.2pm long as compared to the Sn–R bonds of 217.3 and 218.9 pm. 86 D.A. ArmitageO + (Me3Si)3SiLi But But Si Si But But SiMe3 SiMe3 But But SiMe3 Me3Si Si But But Me3Si Me3Si 4 Si SiMe3 But Me3Si But 220 °C Si But ButO Me3Si SiMe3 H But 5a Si But Me3Si ButO SiMe3 But 5b + H ButOH Scheme 2 Si SiMe3 Me3Si Me3Si SiMe3 Si Ph Ph Si Si Ph Ph Me3SiC CSiMe3 PhSi SiPh Me3Si SiMe3 120 °C 6 7 8 (2) The C–B bonds are short, indicating ylidic character (Sn`–C~) of the Sn––C bond (Scheme 3).12 The molybdenum amide [R(R@)N] 3 Mo reacts with CO, the adduct reductively couples with Bu5COCl to give the carbidopivalate 11 which with sodium forms the 87 Carbon, silicon, germanium, tin and leadB (Me3Si)2C B C: But But B (Me3Si)2C C But B But 9 R2Sn: B (Me3Si)2C B C But But SnR2 10 Scheme 3 [R(R¢)N]3Mo R(R¢)N = L L3MoCO L3Mo C O C O But CO 11 L3Mo CH L3Mo C–K+ 2 L3Mo C– L¢ 2K + L¢ PhCH2K L¢ = benzo-15-crown-5 13 12 Scheme 4 carbide (dC 274.2) which can be protonated with MeCN giving 12.Compound 12 is deprotonated by PhCH 2 K to give the carbide dimer which with benzo-15-crown-5 gives 13 (Scheme 4).13 The structure shows a Mo–C bond of 171.3 pm, supporting multiple bond character. The first transition-metal–germanium triple bond 14 results from the coupling of 2,6-(mes) 2 C 6 H 3 GeCl and Na[MoCp(CO) 3 ] in THF through decarbonylation at 50 °C.The Mo-Ge-R skeleton is almost linear (172.2°) with the Mo–Ge bond 227.1 pm, a shortening of 35pm from the single bond length14 [equation (3)]. Na[CpMo(CO)3] + [2,6-(mes)2C6H3]GeCl Cp(CO)2Mo Ge[C6H3(mes)2-2,6] THF, 50 °C –CO (3) The tetrasilacyclobutene (Bu5Me 2 Si) 6 Si 4 15, with a Si––Si bond length of 217.4pm (shorter than in disilenes), is non-planar and photolyses to the bicyclobutane 16, suggesting intermediacy of the tetrasilabuta-1,3-diene.The first such compound 17 88 D.A. ArmitageR2Si RSi SiR SiR2 R2Si RSi SiR2 SiR 15 16 hn dark R = ButMe2Si results from the coupling of (Tip) 2 Si––Si(Tip)Li with its bromide. It melts at 237 °C without decomposition and has Si–Si bond lengths of 217.5 and 232.1pm [equation (4)].15 The former is longer than expected for double and the latter shorter than single, indicating some degree of delocalisation.This is supported by the electronic spectrum. Si Si Tip Tip Si Si Tip2 Tip2 17 Tip = 2,4,6-Pri 3C6H2 (4) Tip2 Si(Tip)Li + Tip2Si Si(Tip)Br The cyclotrigermene (Bu5 3 Si) 4 Ge 3 reacts with [Ph 3 C][BPh 4 ] to give the cyclotrigermenium cation with a 2n electron system. The Ge–Ge bond lengths of 233pm are intermediate between double (224 pm) and single (252 pm), supporting delocalisation. 16 Reducing 2,6-(mes) 2 C 6 H 3 GeCl with KC 8 gives the cyclotrigermenyl radical as blue crystals with Ge–Ge bonds of 235 pm. EPR spectroscopy suggests that the odd electron occupies one of an e-pair of n antibonding orbitals, as indicated by the low hyperfine coupling. Further reduction of this radical with KC 8 gives the ring-opened trigermenyl allyl anion K[2,6-(mes) 2 C 6 H 3 Ge] 3 as dark green crystals with a wide Ge–Ge–Ge angle of 159° and Ge–Ge bonds of 242.2pm which are only slightly shorter than the single bond lengths (244 pm).17 Reducing [2,6-(2,4,6-Pr* 3 C 6 H 2 ) 2 C 6 H 3 ]ClSn: (RClSn) with KC 8 gives the radical anion [RSnSnR]·~ as a potassium complex, the structure indicating a Sn–Sn bond of 281.2 pm.This could be considered as a reduced valence isomer of distannyne with a C–Sn–Sn angle of 95.2°, suggesting lone pair localisation at Sn rather than n bonding. However the neutral distannyne has not as yet been isolated for comparison.18 Tin(II) chloride reacts with R 2 Sn to give either R 2 SnCl 2 and Sn, or RSnCl, depending on R.The reaction of R 2 Sn: [R––CH(Me 3 Si)C 9 H 6 N-8] with SnX 2 (X\F, Cl, Br or I) gives R 2 SnX 2 and Sn but, with SnCl 2 , the intermediate Sn–Sn adduct can be isolated with a Sn–Sn bond of 296.1pm which is significantly longer than that in distannenes.19 Reducing Ph 2 SnCl 2 with lithium in liquid ammonia gives the salt [Li(NH 3 ) 4 ] 2 - [Ph 2 SnSnPh 2 ] as ruby-red crystals.A structure determination shows a centosymmetric anion with Sn–Sn bonds of 291 pm.20 The recent synthesis of 1,2-dimethyl-o-disilaborane (Me 2 Si 2 B 10 H 10 ) and its desilylation with base to give MeSiB 10 H 10 3~ has led to the isolation of n complexes analogous to the carbollides using the Cp*M (M\Co, Rh or Ir) residue. The structure of the rhodium complex shows the Rh–Si bond to be a little longer than the Rh–B bonds.21 The reaction using MeSiB 10 H 11 2~ and MeSiB 10 H 10 3~ in the ratio 2: 1 with FeBr 2 ·DME gives the derivative K 2 [HFe(MeSiB 10 H 10 )] 2 in which the iron atoms each sit above the silaborane clusters with Si–Fe 220.9pm and Fe–B 216–217.3 pm.The iron atoms are linked through a Fe–Fe bond of 242.3pm with 89 Carbon, silicon, germanium, tin and leadhydrogen bridging both Fe–Si and Fe–B bonds.22 Calculations indicate that deprotonation of the parent o-disilaborane would lead to one silicon atom being pushed out of the icosahedral surface and one being pushed slightly into it.23 Reacting B 10 H 10 2~ with Ph 2 SnCl 2 gives substitution of the proton in the 2 position, the crystal structure indicating a B–Sn bond of 218.2 pm.24 The compounds Na 2 MC 2 (M\Pd or Pt) results from reaction between sodium carbide and the metal and show a linear polymer structure for the M–C 2 repeating unit.25 At 1530 K, barium, germanium, and carbon or alternatively BaC 2 and BaGe 2 combine to give Ba 3 Ge 4 C 2 .It is a moisture-sensitive semiconductor and reacts with ammonium chloride to give acetylene and germanes up to Ge 4 Hn.The structure indicates the presence of tetrahedral Ge 4 4~ (Ge–Ge 251.7 pm) and C 2 2~ anions (C–C 120 pm).26 The germanium cluster Ge 9 4~ as its Cs or Pb salts can be formed directly from the elements. The anion has the expected monocapped square-antiprism structure with the Ge–Ge distances being longer within a rectangular plane than between them. The germanidesM 4 Ge 9 andM 12 Ge 17 (M\Na, K, Rb or Cs), also result directly from the elements, the structure of the latter comprising Ge 9 4~ and Ge 4 4~ anions in the ratio 1: 2.The analogous tin clusters can be prepared similarly.27 The anion Sn 9 4~ reacts with elemental tellurium to give the anion [Te 2 Sn(k-Te) 2 SnTe 2 ]4~ and possesses a D 2$ structure.28 The stannide Zr 5 CuSn 3 comprises CuZr 6 octahedra face-bridged as a polymer with tin atoms sitting above the faces of these octahedra.29 The first structurally authenticated bis(indenyl)lead(II) compound [PbM1,3- (Me 3 Si) 2 C 9 H 5N2 ] results from PbI 2 and crystallises with five-membered rings almost eclipsed, almost parallel, and the six-membered rings at about 80° to each other.The arrangement minimised Me 3 Si clashes and with the arene rings. The sandwich compound Cp 2 Pb reacts with 2-C 5 H 4 NLi in THF to give the tris(2-pyridyl) derivative [Pb(2-C 5 H 4 N) 3 Li·THF] in which Li is co-ordinated to the three nitrogen atoms and THF, and with lead, with a stereochemically active lone pair, to the three 2-C atoms of the pyridyl groups.30 Reacting gaseous silane with hydrogen peroxide vapour at low pressure gives commercially valuable planarised silica layers on silicon wafers and probably occurs through a free radical mechanism on the surface.31 The rapid redistribution of (RO) 3 SiH occurs in the presence of dimethyltitanocene to give silane which itself reacts with the catalyst to give blue crystals of [Cp 2 Ti(k-HSiH 2 )] 2 18.This slowly decomposes in solution to give yellow-green crystals of Cp 2 Ti(k-H)(k-HSiH 2 )TiCp 2 19. Both structures contain bridging silyl groups [equation (5)]. The structures were confirmed H Cp2Ti Si H TiCp2 Si H H H H 18 Cp2Ti H Si TiCp2 H H H 19 (5) by comparison of the NMR spectra with those of the monophenyl substituted silyl analogues which have been characterised by X-ray crystallography.32 The bis(silane) (HSiMe 2 ) 2 X (X\C 6 H 4 or O) complexes with (Cy 3 P) 2 RuH 2 (H 2 ) 2 to displace two moles ofH 2 and yield 20 with the bis(silane) bonded through g2-Si–Hbonds [equation 90 D.A.ArmitageSi X Si H H Ru H H PCy3 PCy3 (Cy3P)2Ru(H)2(h2-H2)2 (Me2SiH)2X X = O, o-C6H4 (6) 20 (6)]. The Ru–(g2-H–Si) unit shows a peak at 1778cm~1 in the infrared spectrum and J S*H of 63 Hz (in range for g2-Si–H).33 The structure was confirmed by X-ray di§raction.Heating barium, neodymium, and Si(NH) 2 (from NH 3 and SiCl 4 ) to 1650 °C gives the nitridosilicate Ba 2 Nd 7 Si 11 N 23 with a zeolite-like structure showing wide Si 8 N 8 channels co-ordinating Ba2`. It comprises SiN 4 tetrahedra with Si–N bonds of 167–175pm and is the first example of a nitridosilicate.34 Reaction of Bu5NHSiCl 3 with BuLi gives the tetrachlorocyclodisilazane on warming while halogen exchange with LiF led to the tetrafluoro analogue.Both possess planar Si 2 N 2 rings.35 The salt (Cl 3 Si) 2 NLi mono- and di-substitutes TiCl 4 while with WCl 6 the mixed amide–imide Cl 3 SiN––WCl 3 [N(SiCl 3 ) 2 ] results through SiCl 4 elimination.36 The structure of (Me 2 N) 3 SiH shows non-standard conformation of the irregular orientation of Me 2 Ngroups.The morpholino derivatives (morph) 3 SiX (X\Cl, Me or CH–– CHPh) show a propeller-like structure with C 37 symmetry. The Si–N bonds increase [169 (X\Cl), 170.8 (X\H), 170.9 (X\CH–– CHPh) and 171.2pm (X\Me)] with planar configuration at nitrogen.37 Tetrakis(morpholino)- and 4-methylpiperazino-silanes result from SiBr 4 and amine/lithium amide through the monobromo intermediate tris(amino)bromosilane.They show localised D 2$ symmetry for the Si(CN 2 ) 4 unit. The compound (Me 2 N) 4 Si can be deaminated with triflic acid, the monotriflate reacting with substituted anilines and Et 3 N to give RNHSi(NMe 2 ) 3 (R\2,4-F 2 C 6 H 3 or 4-BrC 6 H 4 ). The 4-bromo derivative redistributes to give (4-BrC 6 H 4 NH) 2 Si(NMe 2 ) 2 .38 The amide (Bu5NH) 2 Si(NLiMe) 2 is tetrameric with three di§erent modes of lithium co-ordination. 39 The compound Bu5 3 PbNH 2 results from its iodide and NaNH 2 , and can be deaminated with aniline. It is a solid and lithiation followed by silylation gives Bu5 3 PbNHSiMe 3 .40 Heating silicon and phosphorus with silver or gold gives the ternary systems Ag 2 SiP 2 and AuSiP.The former possesses a structure in which SiP 4 tetrahedra share corners (Si–P 224.5 pm). Each phosphorus is also bonded to three silver ions and each silver to three phosphorus atoms in a trigonal-planar arrangement. The compound AuSiP shows gold bonding in a linear manner to phosphorus and silicon with the phosphorus tetrahedron completed by three silicon atoms and the silicon tetrahedron by three phosphorus atoms.The Si–P bond lengths are 225.8 pm.41 Silylation of the lithiated diphosphadiboretanes 21 with SiCl 4 gives the spiro derivative [equation (7)]. The reaction is thought to take place in a stepwise manner, since the triphosphamonochloro intermediate has been characterised.42 Chlorophosphanes couple with trichlorosilane in the presence of Et 3 N to give the silyl(phosphanes) in high yield.Bis(trichlorosilyl)phosphanes, PR(SiCl 3 ) 2 , result similarly but are only stable if R is bulky. The structures of the amino derivative (R\Pr* 2 N) shows phosphorus in a pyramidal environment but with planar nitro- 91 Carbon, silicon, germanium, tin and leadBut(R)Si F F Si(R)But HP But(R)Si F Si(R)But P Li(THF)2 F BunLi THF But(R)Si F Si(R)But P 24 Si(R)But F But(R)Si P 24 313 K heat –LiF Scheme 5 HP B P Li B NR2 R2N 21 SiCl4 ButLi R2N B P P B R2N NR2 P Si B NR2 B P (7) gen.43 The analogous trichlorogermyl phosphanes result through insertion of Cl 2 Ge·diox into the P–Cl bond of the chlorophosphane or through condensation of phosphanesRPH 2 with GeCl 4 , together with a range of Ge–P heterocyclic products.44 Sn RP Sn P R Sn PR Sn P R Sn Sn RP RP Cl Sn P Sn Cl Sn P R R 22 R = Pri 3Si 23 R = Pri 2(2,4,6-Pri 3C6H2)Si Tin(II)–phosphorus clusters result from the coupling of primary silyl phosphines R 3 SiPH 2 with R 2 Sn: [R\(Me 3 Si) 2 N or 2,4,6-(CF 3 ) 3 C 6 H 2 ].The cluster [(Pr* 3 Si)PSn] 6 22 results almost quantitatively and contains a distorted hexagonal prism.With R 2 Sn:/SnCl 2 , the SnCl 2 adduct of the dimers result, [MPr* 2 (2,4,6- Pr* 3 C 6 H 2 )NSiPSn] 2 SnCl 2 23, with SnCl 2 bridging the dimer.45 Lithiation of the silylphosphine HP(SiBu5RF) 2 followed by loss of LiF gives Bu5RSiFP––SiRBu5 24 which undergoes a 1,3-sigmatropic fluorine migration and shows Si–P bond lengths of 205.3 and 220.7pm (Scheme 5).It can be lithiated at the Si–P double bond to give further loss of LiF and gives 25 and 26 as a mixture [equation (8)].46 Metallo-substituted phosphasilanes (2,4,6-Pr* 3 C 6 H 2 ) 2 Si(F)P(H)–M [M\CpFe(CO) 2 , Cp*Fe(CO) 2 or Cp*Ni(PPh 3 )] result from the fluorosilyl phosphanide and metal bromide and can be lithiated at P. Thermolysis of the former gives 92 D.A.ArmitageBut(R)Si P Si(R)But Li(thf)+ x – 24 2Li heat HP Si Si HP Si O Si R But R But But R R But 25 26 40 °C H+ (8) the P-ferrio phosphasilene (2,4,6-Pr* 3 C 6 H 2 ) 2 Si––PFe(CO) 2 Cp which has been characterised in solution.47 The low-temperature pyrolysis of M[OSi(OBu5) 3 ] 4 (M\Zr or Hf) gives homogeneous zirconia- and hafnia-silica,MO 2 ·4SiO 2 . The precursors occur as a mixture of isomers containing both four- and five-co-ordinate M, the latter involving an g2- OSi(OBu5) 3 ligand.48 The relatively acidic Ph 3 SiOH reacts with [M(OBu5) 2 ]n (M\Ge or Sn, n\2; M\Pb, n\3) to give [Ph 3 SiOM(k-OBu5)] 2 with planar M 2 O 2 rings.49 The compounds readily complex with metal carbonyl residues as does Sn 6 (k3 -O) 4 (k3 -OSiMe 3 ) 4 which comprises an octahedral cage of tin atoms facially bridged by the oxygen ligands.50 Ge O N mes C Tbt Tip 27 Heating silver and germanium oxides in the presence of a little water gives the trigermanate Ag 8 Ge 3 O 10 in which the anion contains four-co-ordinate germanium with Ge–O bonds in the range 170–183 pm.51 The first oxazagermete 27 results from the [1]3]cycloaddition of the hindered germylene Tbt(Tip)Ge: with mesitonitrile oxide.A structure determination indicates a planar four-membered ring, its strain being reflected in the small angle at germanium (C–Ge–O 68.7°) and the long Ge–O bond (187.2 pm).52 Heating gives the germanone which adds to dienes. The tin(II) phosphate [H 3 NCH 2 CH 2 NH 3 ][Sn 4 P 3 O 12 ] 2 shows an open cage structure with eight-membered P 2 O 4 Sn 2 rings interconnected through Sn–O–P bridges.52 The lanthanides Ln 4 [Al 12 O 24 ][Pb 4 O 4 ] (Ln\Nd or Sm) show Ln3` bonding within four of the eight six-membered rings of AlO 4 tetrahedra with Pb 4 O 4 units incorporated into the sodalite Al 12 O 24 framework and co-ordinating to two pairs of opposite lanthanide ions.54 The reductive dimerisation of carbon disulfide followed by C––S insertion and isomerisation then reaction with CS 2 /Me 4 NF in DMF gives the anion C 4 S 7 2~ 28 (Scheme 6).55 Reducing C 4 S 6 29 with sodium in liquid ammonia gives Na 2 C 4 Sx which with Ph 4 PCl precipitates purple-red crystals of [Ph 4 P] 2 C 4 S 8 30 [equation (9)].However, with the tricyclic dithiocarbonate C 6 S 8 O 2 31 and NaOMe, extraction of the Na 2 C 4 Sx mixture with [N(PPh 3 ) 2 ] Cl gives [N(PPh 3 ) 2 ] 4 [C 16 S 18 ] 32 which spontaneously loses sulfur to produce polymeric [(C 8 S 8 )n]2n~ (Scheme 7).56 93 Carbon, silicon, germanium, tin and lead4 CS2 2 [C2S4]2– S S S –S –S S S –S –S S S S –S S S C S S – FCS2 – –F– 28 4e– DMF –[CS3]2– Scheme 6 S S S S S S S S S S S S S– S– 30 29 NaC4Sx Na/NH3 [Ph4P]Cl (9) S S O S S O S S S S 31 1 2 [C8S9]2– + 2(MeO)2CO + 1 2 S7 4MeO– [C16S18]4– [N(PPh3)2]Cl (C8S8) n 2 n– S S S S S –S S S– S S S S S– S– S S S S 32 Scheme 7 Carbon monosulfide results on irradiation of carbon disulfide in argon.Depositing at 10K with CO followed by further irradiation at 254nm (wavelength at which CS absorbs) gives 2-thioxoethen-1-one S–– C––C––O with stretches observed at 2156 and 1505 cm~1 as predicted from calculations.Decomposition occurs on irradiation at 313 nm.57 94 D.A. ArmitageS S S S I I MeS MeS S S S S MeS MeS (IF2C)2 S S S S X X MeS MeS LDA (XCl2C)2 (10) 33 X = Cl, Br Bis(methylthio)tetrathiofulvalene 33 can be readily halogenated at the exposed double bond using hexahalogenoethanes [equation (10)].58 Tetramethyltetrathiafulvalene gives charge-transfer complexes with cyananilic acid (2,5-dicyano-3,6-dihydroxy- p-quinone) with one-dimensional antiferromagnetic character.59 Compound 34 forms a range of phases with iodine that exhibit high conductivity.The structure is consistent with a charge of ]1.67 for the donor which forms uniform stacks responsible for the conductivity. The anions occur as discrete I 3 ~ and infinite chains of I 3 ~.60 S S S S S S S S MeS MeS SMe SMe 34 RM MR E E RM MR E E E E 9 10 7 8 1 2 3 4 5 6 35 R = Me2CHCMe2 RM E MR E MR E E E R M E 36 E M E M E M E E M E 10 8 1 2 9 3 4 5 6 7 Tetrathiafulvalene chemistry has been reviewed61 and the electronic properties of a range of metal derivatives of its dithiols have been studied.62 The bis(ethylenedithio) derivative undergoes photoinduced electron transfer to C 70 .63 A similar range of diselenathiafulvalene derivatives has been synthesised.64 Di-tert-butylsilylene can be generated from the photolysis of the trisilane and reacts with selenophene or 2,5-dimethyltellurophene through chalcogen abstraction to give diselena- and ditellura-2,4-disiletane in which the rings are planar.65 The compound Me 2 CHCMe 2 MCl 3 (M\Si or Ge) reacts with Li 2 E (E\S or Se) to give the cage chalcogenides with non-adamantane tricyclo[5.1.1.13,5] tetrasila- and -tetragermahexachalcogenanes 35.These strained double-decker structures revert to the [3.3.1.13,7]adamantane structures 36 on heating the sulfides at 190 °C, and the sele nides at 80 °C. The structures show the M[E bonds are slightly longer in the less thermally stable, non-admantane-like isomer.66 Reacting germanium and selenium with silver acetate in the presence of alkali-metal carbonates gives the open framework cluster M 3 [AgGe 4 Se 10 ]·2H 2 O (M\Rb or Cs) comprising four adamantane-like Ge 4 Se 10 units interacting with each Ag`.67 The tetraselenastannolane 37 reacts with Ph 3 P to give both stannaneselone and diselenastannirane, depending on the amount of phosphine used.Both are stable, the structure of the former having a Sn–Se bond length of 237.5 pm, some 15pm shorter 95 Carbon, silicon, germanium, tin and leadthan those of the diselenastannirane. The geometry at tin in the stannaneselone is planar.68 The red plumbanethiones Tbt(R)Pb––S, which are stable below [20 °C, readily add to (mes)CNO or PhNCS to give the heterocycles 38 and 39.Above[20 °C, they dimerise to the yellow cyclodiplumbadithiane.69 Se Se Sn Se Se Tbt R Pb S C S Tbt R NPh S Pb O N Tbt R Mes 37 38 39 Heating K 2 Te with the elements gold, silver, tin and tellurium to 800 °C gives small yields of the anion [Au(Ag 1~xAux) 2 Sn 2 Te 9 ]4~ as the Et 4 N` salt. It shows conductivity through the (–Au–Te–Te–Te–) polymer strand that forms part of the 1-D polymer comprising the SnTe 4 tetrahedra complexed to gold and silver.70 Reducing GeF 4 with Ge at 300 °C gives the hygroscopic Ge 7 F 16 which comprises [Ge 6 F 10 ]2` and GeF 6 2~ ions.The Ge2` cations within the sheets are co-ordinated to three fluoride ions as distorted trigonal pyramids with Ge–F bonds between 183 and 218 pm.The sheets are bridged by GeF 6 octahedra and the compound forms the first member of the series Gem 4`Gen 2`F 4m`2n (m\1, n\6).71 Germanium(II) chloride readily inserts into the M–Cl bond (M\Mo or W) of RM(CO) 3 Cl (R\Cp or Cp*) or cis-CpMo(L)(CO) 2 Cl. The compound cis- CpMo(CO) 2 (PMe 3 )GeCl 3 isomerises in solution. Dichlorogermyl complexes result equally readily from a similar insertion into CpMo(CO) 3 H and slow chlorination to the trichloro derivative occurs in dichloromethane.72 With Ph 2 PCH 2 PPh 2 (dppm) stabilised gold(I) chloride, insertion of GeCl 2 occurs to give [Au 2 (dppm) 2 ]- [MAu(GeCl 3 ) 2N2 ] which slowly decomposes to give [Au 2 (dppm) 2 ][Au(GeCl 3 ) 3 ].73 A range of monodentate and chelating selenides complex with SnX 4 to give six-coordinate complexes.Those of chelating ligands occur as meso and DL forms.74 References 1 R.R. Tykwinski and F. Diederich, Liebigs Ann. Chem., 1997, 649; U. H. F. Bunz, Synlett, 1997, 1117. 2 M.M. Haley, S. C. Brand and J. J. Pak, Angew. Chem., Int. Ed. Engl., 1997, 36, 836. 3 M.P. Gamasa, J. Gimeno, C. Gonzalez-Bernardo, J. Borge and S.Garcia-Granda, Organometallics, 1997, 16, 2483. 4 M. Brady, W. Weng, Y. Zhou, J. W. Seyler, A. J. Amoroso, A. M. Arif, M. Bohme, G. Frenking and J. A. Gladysz, J. Am. Chem. Soc., 1997, 119, 775. 5 J.B. 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ISSN:0260-1818    

DOI:10.1039/ic094085

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

7 Nitrogen, phosphorus, arsenic, antimony and bismuth By K. K. HII and T. P. KEE School of Chemistry, University of Leeds, Leeds LS2 9JT, UK 1 Introduction This report covers important aspects in the development of Group 15 chemistry during the year 1997.1 Since a comprehensive reviewis unfortunately beyondthe remit of this particular article attention has been focused on the twin areas of metalloorganic and co-ordination chemistry.Within the area of phosphorus chemistry, only synthetic work on novel asymmetric phosphines and derivatives is described with particular emphasis on applications in asymmetric catalysis. 2 Nitrogen Studies have been reported on the design of chiral bidentate lithiumamides and chiral tetradentate amines, and the use of these chiral bases for enantioselective formation and the reactions of lithium enolates has been explored. Chiral bidentate lithium amides having a chiral amide nitrogen by virtue of chelation were successfully applied to the enantioselective deprotonation reaction of prochiral cyclic ketones, the kinetic resolution of racemic cyclohexanone derivatives by deprotonation, and the regioselective deprotonationof optically active 3-keto steroids.Structures of some of these chiral bidentate lithium amides in the solid state and in solution were elucidated by X-ray di§raction and NMR spectroscopic analyses. By use of chiral tetradentate amines, enantioselective reactions of lithium enolates with electrophiles, such as alkylation, protonation, and Michael addition, proceeded successfully.Examples of catalytic enantioselective deprotonation, alkylation, and protonation by the present strategy have also been presented and discussed.2 The synthesis of a new optically active aminophosphine ligand containing a potentially stereogenic nitrogen atom, from (S)-N-isopropyl-N-methyl-a-methylbenzylamine has been described and its complex with palladium(II) chloride has been obtained.NMR spectroscopy revealed that the co-ordination of the aminophosphine to the metal resulted in stereospecific locking of the donor-nitrogen atomin only one of two possible configurations.3 Mononuclear complexes of the type [Cu(valp) 2 (bipy)]·H 2 O, Cu(valp) 2 (phen) and Cu(valp) 2 (dmphen); and polynuclear complexes of the type [Cu(valp) 2 (k-4,4@-bipy)]n 99and [Cu 2 (valp) 4 (k-4,4@-bipy)]n have been synthesized and characterized by magnetic and spectroscopic measurements. Spectral and magnetic data are consistent with mononuclear structures. The copper atom in [Cu(valp) 2 (bipy)]·H 2 O, and Cu(valp) 2 (phen) is co-ordinated to two nitrogen atoms from diimine, and by two asymmetric carboxylic oxygen atoms from each bidentate valproate ion to give a tetragonally elongated CuN 2 O 2 ]O 2 chromophore.The copper atom in Cu(valp) 2 (dmphen) is co-ordinated to two nitrogen atoms from dmphen, two carboxylic oxygens of a bidentate valproate ion, and an oxygen atom of a monodentate carboxylic group of a second valproate ion to give a highly distorted square pyramid or trigonal bipyramid CuN 2 O 3 chromophore.The data for [Cu(valp) 2 (k-4,4@-bipy)]n and [Cu 2 (valp) 4 (k-4,4@-bipy)]n indicate that these complexes are polymeric in which the nitrogen atoms of 4,4@-bipy bridge mononuclear Cu(valp) 2 moieties, co-ordinate equatorially in [Cu(valp) 2 (k-4,4@-bipy)]n, bridge binuclear Cu(k-valp) 4 Cu moities and co-ordinate axially in [Cu 2 (valp) 4 (k-4,4@-bipy)]n.4 V O O H2 N H2 N NH2 O O O 1 V O O H2 N H2 N NH2 O O O 2 OH V O O H2 N H2 N NH2 O O NH2 3 –O O + V H2N O O N O H2N N 4 NH HN A novel series of vanadium(V) hydroxylamido complexes with weak ligands including glycine, [VO(NH 2 O) 2 (Gly)]·H 2 O 1; serine, [VO(NH 2 O) 2 (Ser)]·H 2 O 2; glycylglycine, [VO(NH 2 O) 2 (Gly-Gly)]·H 2 O 3; and imidazole, [VO(NH 2 O) 2 (Him) 2 ]Cl 4 have been prepared and characterized both in solution and in the solid state.The vanadium atom in these four complexes is seven-co-ordinate with pentagonal bipyramidal geometry. In the first three complexes, the hydroxylamido groups are co-ordinated side-on with the hydroxylamido nitrogen cis to the organic ligand in the equatorial plane. In the fourth complex, the hydroxylamido groups are co-ordinated side-on with the hydroxylamido nitrogen trans to the imidazole ligand in the equatorial plane.The UV/VIS spectra of these complexes were also examined, and found to show similarities with those of the vanadium(V) hydroxylamido complexes and known side-on peroxovanadium complexes. Multinuclear NMR studies were conducted to characterize the solution structure and properties of these compounds. The salt [VO(NH 2 O) 2 (Him) 2 ]Cl was found to be less labile and more stable than the corresponding diperoxovanadium(V) imidazole complex, H[VO(O 2 ) 2 (Him)].In solution the inherent asymmetry of the hydroxylamido ligand has facilitated an in-depth study of ligand exchange. Upon dissolution, [VO(NH 2 O) 2 (Him) 2 ]Cl forms three isomeric complexes, all of which have one of the original two-co-ordinated imidazole groups in the complex dissociated. 1-D and 2-D EXCSY and multinuclear NMR spectroscopy was used to examine the stoichiometry of the isomers, their structures, and the dynamics of their ligand exchanges. Specifically; both inter- and intra-molecular exchanges were observed for [VO(NH 2 O) 2 (Him)]Cl involving both the co-ordinated 100 K.K. Hii and T.P. Keeimidazole and the co-ordinated hydroxylamido groups.The intra-molecular exchange of the co-ordinated imidazole in H[VO(O 2 ) 2 (Him)] was compared to that in the hydroxylamido complex, and the hydroxylamido compounds were found to have some properties that may be advantageous over those of the diperoxovanadium(V) complexes.5 N N N Co N O O N+ N+ O O O O – – 5 N N L1 Five new compounds of the ligand 1,2-bis(2-pyridyl)ethyne L1, [ML1(NO 3 ) 2 ]n (M\Co, Ni or Cu), [ZnL1Cl 2 ]n and [CuL1 3 (NO 3 ) 4 ] have been described.The first four compounds, prepared from the ligand and the metal salts in ethanol, acetone or tetrahydrofuran, are infinite chain compounds in the solid state with the ligand serving to bridge the metal centers solely through the pyridine nitrogen atoms.A crystal structure of [CoL2(NO 3 ) 2 ]n 5 showed the polymers to be linear. The donor nitrogen atoms are co-ordinated to the cobalt ion in a cis arrangement with Co–N distances of 2.073(6) and 2.076(6)Å. Each cobalt atom is further co-ordinated by two nitrate ions in an asymmetric chelating fashion with short cobalt to oxygen distances of 2.020(10) and 2.011(9)Å and two longer contacts at 2.473(13) and 2.458(12)Å.6 A series of monomeric palladium amido complexes of the form trans- (PPh 3 ) 2 Pd(R)(NR@2 ) and (dppf)Pd(R)(NR@2 ) have been prepared by the reaction of lithium and potassium amides with palladium aryl halide complexes.A crystal structure of (dppf)Pd(p-Me 2 NC 6 H 4 )[N(p-CH 3 C 6 H 4 ) 2 ] was obtained. Upon thermolysis in the presence of PPh 3 , serving as a trapping agent, these monomeric palladium amido complexes underwent C–N bond-forming reductive elimination to form arylamines in high yields along with a Pd0 species.Reductive elimination was also observed from the azametallacycle (PPh 3 )Pd(g2-C 6 H 4 C 6 H 4 NH), to form carbazole and Pd(PPh 3 ) 4 at room temperature. Mechanistic studies on the reductive elimination reactions of the monomeric PPh 3 -ligated amido complexes indicated the presence of two competing pathways for the formation of amine.At low [PPh 3 ], reductive elimination occurred via phosphine dissociation to form a three-co-ordinate intermediate; however, as [PPh 3 ] was increased, a pathway of reductive elimination from a four-co-ordinate complex became dominant.The dppf-ligated palladium amido complexes directly eliminated amine from the four-co-ordinate complex. The mechanism of the reductive elimination from dimeric palladium amido complexes was also studied. These complexes underwent reductive elimination of amine via dimer dissociation to generate three-co-ordinate intermediates analogous to those formed by the PPh 3 -ligated 101 Nitrogen, phosphorus, arsenic, antimony and bismuthmonomeric amido complexes.The C–Nbond-forming reductive elimination reactions were accelerated by electron-withdrawing groups on the Pd bound aryl group and by electron-donating groups on the amido ligand, suggesting that the aryl group acts as an electrophile and the amido ligand acts as a nucleophile.7 Fe Ph2P Me2N Me L2 Fe Ph2P Me2N H L3 (Aminoferrocenyl)phosphine ligands 2-[1-(dimethylamino)ethyl]-1-(diphenylphosphino) ferrocene L2 and (g5-cyclopentadienyl)[g5-4-(endo-dimethylamino)-3-diphenylphosphino- 4,5,6,7-tetrahydro-1H-indenyl]iron(II) L3, have been used as ligands for palladium-(0) and -(II) complexes.The reaction of Pd 2 (dba) 3 ·CHCl 3 with L2 or L3 in the presence of the electron-withdrawing olefins maleic anhydride and dimethyl fumarate gave the complexes Pd(L3)(DMFU), Pd(L2)(MA), and Pd(L2)(DMFU).Allylic complexes [Pd(g3-2-MeC 3 H 4 )(L3)]OTf and [Pd(g3-2-MeC 3 H 4 )(L2)]OTf were obtained by reaction of L3 or L2 with [Pd(g3-2-MeC 3 H 4 )Cl] 2 in the presence of AgOTf. In solution all these compounds exist as mixtures of two diastereomers, with either the alkene or the allyl group di§erently oriented with respect to the aminophosphine ligand. 1H NMR variable-temperature studies were carried out for each of the complexes and for Pd(L3)(MA). Rotation of the alkene was observed on the NMR time-scale. *G8 has been calculated and values between 77.6 kJ mol~1 (373 K) and 76.6 kJ mol~1 (373 K) obtained. A Pd–N bond rupture which interchanges the two amino methyl groups was observed [*G(328)8\63.9 kJ mol~1 to *G(368)8\74.9 kJ mol~1] for derivatives of L2 but not for complexes containing L3.8 Copper(II) complexes of the tripodal ligand tris[(benzimidazol-2-yl)methyl]amine have been synthesized and structurally characterized.Two di§erent solvates of Cu(tbima)(NO 3 ) 2 , [Cu(tbima)(NO 3 )][NO 3 ]·EtOH and [Cu(tbima)(NO 3 )][NO 3 ]· H 2 O, were isolated.The copper co-ordination spheres of the two solvates are signifi- cantly di§erent, and neither displays the most common type of geometries encountered in CuII complexes. In both complexes tbima is a tetradentate ligand, and one of the nitrate groups is co-ordinated in the bidentate, asymmetric mode. The co-ordination geometry in [Cu(tbima)(NO 3 )][NO 3 ]·EtOH is elongated octahedral, but with a very strong tetrahedral distortion of the equatorial plane which is defined by the three benzimidazole nitrogen atoms and one nitrate oxygen atom.In [Cu(tbima)(NO 3 )]- [NO 3 ]·H 2 O the interaction with one of the nitrate oxygen atoms is very weak; the remaining five-co-ordinated atoms create a distorted square pyramidal environment for copper, but the axial bond in the pyramid is not the longest bond, as usually found.9 The preparation and structural characterization of three copper(II) dinuclear complexes of formula [Cu 2 (terpy) 2 Cl 2 (ta)]·4H 2 O, [Cu 2 (bpca) 2 (ita)]·2H 2 O and [Cu 2 (terpy) 2 Cl 2 (phta)]·4H 2 O have been described.10 A family of enantiomerically pure (1R,2R)-1-(dialkylamino)-1-phenyl-3-(R-oxy)-2- 102 K.K.Hii and T.P. KeePh OR¢ OH NR2 L4 R;R¢ = various organic propanols L4 have been synthesized from (2S,3S)-2,3-epoxy-3-phenylpropanol, arising from the Sharpless epoxydation of cinnamyl alcohol, by two alternative sequences involving either the regioselective ring opening of the epoxide by a secondary amine and subsequent chemoselective protection of the primary hydroxy group, or by the reverse of these operations.A total of 19 di§erent pure (1R,2R)-1-(dialkylamino)-1- phenyl-3-(R-oxy)-2-propanol derivatives have been prepared in an iterative process aimed at the optimization of their catalytic properties in the enantioselective addition of diethylzinc to benzaldehyde. In doing this, the steric bulk of the R-oxy group and the choice of the dialkylamino substituent as a nitrogen-containing six-membered ring have been identified as the key structural parameters for high catalytic activity and enantioselectivity involving this class of ligand.11 H3C N H CH2OMe Ph H H Ph L5 It has been shown by the use of multinuclear and multidimensional NMR that the reaction mixture of lithium, [2-methoxy-(R)-1-phenylethyl][(S)-1-phenylethyl]amine L5 and cyclohexene oxide in diethoxyethane results in the formation of monomeric and dimeric complexes between the amide molecule and cyclohexene oxide at[80 °C.The dimeric complex of [2-methoxy-(R)-1-phenylethyl][(S)-1-phenylethyl]amide exhibited a slow cyclohexene oxide substitution rate on the NMR time-scale that was found to be controlled by a dissociative mechanism.The 6Li–1H NOESY NMR spectrum of the above reaction mixture showed NOEs between lithium and cyclohexene oxide protons in both the monomeric and dimeric complexes of [2- methoxy-(R)-1-phenylethyl][(S)-1-phenylethyl]amide. A number of further solution and solid phase structural experiments were described.12 Chiral cobalt–diamine complexes have been prepared and tested in the catalytic reduction of b-ketoesters and -ketones with molecular hydrogen or hydride transfer reduction (HTR). Modest to high conversions, but low enantioselectivities (e.e.s) were obtained in the first case whereas encouraging e.e.s (up to 58%) but low conversions were observed in the reduction of acetophenone by HTR.The synthesis of chiral nitrogen tetradentate ligands for Co, Ir and Rh have been described.Furthermore, (1R,2R)-([)-N-tosylethane-1,2-diamine proved to be a particularly e¶cient ligand for iridium in the hydride transfer reduction of acetophenone (87% conversion, 92%e.e.).13 In attempts to form extended chains Ru 2 [O 2 C(CH 2 ) 6 CH 3 ] 4 has been reacted with both simple co-ordination and redox-active bridging ligands.The simple co-ordination ligands, pyrazine and 4-cyanopyridine, were co-ordinated in the axial sites of the diruthenium complex. With the symmetric ligand pyz, the polymer 103 Nitrogen, phosphorus, arsenic, antimony and bismuth[Ru 2MO 2 C(CH 2 ) 6 CH 3N4 (pyz)] was isolated. With the asymmetric ligand cpy, the pyridine nitrogen co-ordinated preferentially and the bis-adduct [Ru 2MO 2 C(CH 2 ) 6 CH 3N4 (cpy)] 2 was isolated.Solution UV/VIS and NMR studies indicated that n interactions between the Ru–Ru n* and ligand n orbitals were occurring in both cases. Mole ratio and continuous variation studies of Ru 2 [O 2 C(CH 2 ) 6 CH 3 ] 4 with pyz and cpy indicated that these axial ligands were labile and that a number of solution species existed. When Ru 2 [O 2 C(CH 2 ) 6 CH 3 ] 4 was reacted with tcne, redox reactions occurred.Solid-state IR and solution NMR studies also showed that Ru 2 [O 2 C(CH 2 ) 6 CH 3 ] 4 [tcne] contained a diruthenium carboxylate core which no longer possessed the D 4) paddle-wheel geometry.14 Tetra(n-butyl)ammonium acetophthalocyaninato(2[)indate(III) complexes of selected bidentate dioxo ligands (oxalate, catecholate, sulfate and carbonate) have been obtained by the reaction of tetra(n-butyl)ammonium cis-dihydroxophthalocyaninato( 2[)indate(III) with oxalic acid, catechol, hydrogensulfate and ammonium carbaminate.The carbonate complex is six-co-ordinated by four isoindole nitrogen atoms and two oxygen atoms of the carbonate in a cis arrangement.15 N O Mn O N O N Mn N O (L) (L) 6 The carrier properties of [Mn(acac-L-en)]-derived compounds 6 toward polar organometallics, inorganic ion pairs, and salts have been examined.Such properties are the consequence of MnII behaving as a Lewis acid and the bite angle of the bidentate Schi§-base ligand toward alkali-metal cations. The starting compounds, which occur in a dimeric form, [Mn(acac-L-en)] 2 [L@\CH 2 CH 2 ; LA\C 6 H 10 ; L@@@\R,R-C 6 H 10 ] have been synthesized either via a metathesis reaction from MnCl 2 or using [Mn 3 (mes) 6 ].The reaction of the above with lithium organometallics allowed the isolation of [Mn(acac-L-en)(R)Li(dme)] [R\Me, L\L@; R\Ph, L\L@; R\mes, L\L@; R\Me, L\LA; R\Me, L\L@@@] as metalated forms, where the alkyl or aryl group is p bonded to MnII and the lithium cation is anchored to the Schi§-base ligand.These metalated compounds react with PhCHO to give the corresponding lithium alkoxide, which remains bound in its ion-pair form to the [Mn(acac- L-en)] skeleton in [Mn 2 (acac-L@-en) 2 Li 2MOCH(Ph)MeN2 ]n. This metalated complex was able to transfer the methyl group to the nitrile function to give the corresponding lithium–imide which remained bonded to [Mn(acac-L-en)] as the ion pair in a dimeric structure as revealed for [Mn 2 (acac-L@-en) 2 Li 2 (dme) 2 ]n.All the dimeric units described showed a slight antiferromagnetic coupling between the two MnII ions assisted by bridging alkoxo groups.16 Reaction of Cp*Ir(CO) 2 with [N 2 R]BF 4 (R\p-C 6 H 4 OMe) in acetone at [78 °C a§ords the nitrogen extrusion product [Cp*Ir(CO) 2 (R)]BF 4 , but in dichloromethane 104 K.K.Hii and T.P. Keeit yields a dinuclear product [Cp*(CO) 2 IrIrCl(CO)Cp*]BF 4 . By carrying out this reaction in ethanol, a nitrogen-retained product [Cp*Ir(CO)(OEt)(NHNR)]BF 4 containing an aryldiazene ligand was obtained. Deprotonation of the latter gives the neutral doubly-bent aryldiazenido complex Cp*Ir(CO)(OEt)(N 2 R) quantitatively.Solution IR, NMR and solid phase X-ray di§raction analyses were reported.17 The structures of the complexes [Pd(g3-allyl)(N–N@)]ClO 4 [allyl\but-2-enyl or 3-methylbut-2-enyl, N–N@\C 5 H 3 NCH––NR@-2-R-6 (R\H, R@\Me, CMe 3 or C 6 H 4 OMe-4; R\Me, R@\C 6 H 4 OMe-4) and C 5 H 4 NCH 2 NMe 2 -2] which are present in solution with di§erent isomers, may be assigned by a 1H NMR criterion based on chemical shift changes of the pyridine; and/or of the allylic methyl protons as confirmed by 2-D 1H NMR spectra.The isomer distribution depends mainly on the steric requirements of both the allyl and N–N@ ligands: for [Pd(g3-allyl)(N–N@)]ClO 4 (allyl\3-methylbut-2-enyl) the predominant isomer (ca. 100%) has a structure with the allylic methyl groups cis to the co-ordinated pyridine nitrogen when N–N@\C 5 H 4 NCH––NCMe 3 -2 and cis to the co-ordinated imino nitrogen when N–N@\C 5 H 3 N(CH–– NC 6 H 4 OMe-4)-2-Me-6.In chlorinated solvents the isomers undergo mutual interconversion through a mechanism involving an apparent rotation of the g3-allyl ligand around its bond axis to the metal. The interconversion rates depend on the nature of allyl and N–N@ ligands and increase considerably when the compounds are dissolved in (CD 3 ) 2 SO.The apparent allyl rotation also occurs for the analogous (g3-2-methylprop-2-enyl)palladium(II) derivatives. For [Pd(R)(N–N@)]ClO 4 [R\2-methylprop-2-enyl,N–N@\C 5 H 3 N(CHNC 6 H 4 OMe-4)-2-Me-6] the allyl rotation rate increases with increasing concentration up to a limiting constant value.This behavior is interpreted on the basis of a mechanism involving a fast and reversible association of the cationic complex with the perchlorate anion to form a loose ion pair which undergoes a rate-determining molecular geometry rearrangement upon coordination of ClO 4 . For a solution of [Pd(g3-R)(N–N@)]ClO 4 (R\3-methylbut-2- enyl, N–N@\C 5 H 4 NCH 2 NMe 2 -2) in (CDCl 2 ) 2 , the 2-D ROESY spectrum suggests that the apparent allyl rotation at 28 °C does not involve Pd–NMe 2 bond breaking.The rupture of this bond takes place when the temperature is raised to ca. 90°C or when the complex is dissolved in (CD 3 ) 2 SO at ambient temperature.18 N PPh2 Me2N 7 3 Phosphorus The phosphorus-containing amidine 7 has been prepared through several steps from L-valine and the new ligand exploited in asymmetric reactions such as the palladiumcatalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate and pivalate with the nucleophile derived from dimethyl malonate.Excellent levels of asymmetric induction up to 95%e.e. were achieved along with an e¶cient conversion.19 The cationic palladium(II) complex containing orthometallated (R)-1-[1- 105 Nitrogen, phosphorus, arsenic, antimony and bismuth(dimethylamino)ethyl]benzene and [1a, 4a, 5a(S), 7R]-[5-(diphenylphosphino)-2,3- dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]-hept-2-enehas been prepared by both the co-ordination of the diphosphine to the organopalladium unit and by the asymmetric Diels–Alder reaction between 1-phenyl-3,4-dimethylphosphole and diphenylvinylphosphine using the organopalladium unit as the reaction promoter.20 Vicinal diarylphosphinites derived from carbohydrates are excellent ligands for the RhI-catalyzed enantioselective asymmetric hydrogenation of dehydroamino acid derivatives, producing the highest enantioselectivity of any ligands directly prepared from natural products.The enantioselectivity can be enhanced by the appropriate choice of substituents on the aromatic rings of the phosphinites.For example, the use of phosphinites with electron-donating bis(3,5-dimethylphenyl) groups on phosphorus provides e.e.s up to 99% for a wide range of amino acids including some with easily removable N-protecting groups. Electron-withdrawing aryl substituents, on the other hand, decrease the enantioselectivity.The sense of chiral induction in the amino acid product depends on the relative juxtaposition of the vicinal diphosphinites on a given sugar backbone. When readily available D-glucopyranosides are used as the starting sugars, 2,3-phosphinites give the S-amino acids and 3,4-phosphinites give the R-amino acids. In the case of aromatic and heteroaromatic amino acids, enantioselectivities [95% are consistently obtained.Practical considerations such as the ease of ligand synthesis, rates of reactions, catalyst turnover, and scope and limitations in terms of substrates have been discussed. A possible explanation for the enhancement of enantioselectivity by electron-rich phosphinites was o§ered.21 P R O N H Br L7 P O N H L6 The Michaelis Arbuzov reaction between the enantiopure 2-phenyl-1,3,2- oxazaphospholidine L6 and di§erent activated halide compounds a§orded with total diastereoselectivity chiral phosphinamides L7.Oxazaphospholidine L6 reacted with a-halogenoacetophenones to give both chiral Michaelis Arbuzov products and a mixture of diastereomers formed from the Perkow reaction. New hybrid phosphine –phosphine oxide ligands were easily obtained from phosphinamides L7, bearing chirality on the carbon chain and the phosphine oxide moiety, or on the carbon chain and the two di§erent phosphorus centers.The co-ordination chemistry of these ligands has been studied with transition metals and Lewis acids.22 H2N P Cl Me L8 The asymmetric bidentate ligand (^)-(2-aminophenyl)(2-chlorophenyl)methylphosphine L8 has been prepared via chemoselective cleavage of the phenyl group from 106 K.K.Hii and T.P. Kee(^)-(2-aminophenyl)methylphenylphosphine using lithium in thf, to give (2- aminophenyl)methylphosphine upon hydrolysis, followed by deprotonation of the secondary phosphine with sodium in thf and subsequent reaction with 1,2-dichlorobenzene. The chlorophenyl-substituted tertiary phosphine has been resolved by the method of metal complexation and the absolute configuration of the R enantiomer assigned by a crystal structure determination of the diastereomeric palladium(II) complex [(S-P),(R)]-[(2-aminophenyl)(2-chlorophenyl)methylphosphine-N,P]palladium( II) hexafluorophosphate.23 N O Me Me PPh2 L9 The chiral amino alcohol, cis-2-amino-3,3-dimethylindan-1-ol, was converted into the corresponding enantiomerically pure phosphorus-containing oxazoline L9 and this oxazoline found to be an e¶cient ligand for palladium-catalyzed enantioselective allylic amination reactions. The amination reaction of (E)-1,3-diphenylprop-2-en-1-yl acetate L10 was found to be more e¶cient than with the similar ligands derived from valinol, tert-leucinol, etc.Other 1,3-bis(p-substituted aryl)prop-2-en-1-yl acetates were also converted into the corresponding amines in a similar manner and with excellent enantioselectivity.24 Ph Ph O O CH3 L10 The enantioselectivities arising from a Pd-catalyzed Heck reaction ([98%e.e.) and an allylic alkylation ([90%e.e.) using a 3,5-di-tert-butyl-MeO-biphep chiral auxiliary L11 have been reported.Higher e.e.s were observed with the 3,5-dialkyl substituents than with the unsubstituted parent MeO-biphep. It is proposed that the observed dialkyl ‘meta-e§ect’ on enantioselectivity is the combined result of a more rigid and slightly larger chiral pocket and that this e§ect will have some generality in homogeneous catalysis. DetailedNMR studies on the allyl complex [Pd(PhCHCHCHPh)(L11)] PF 6 and the model hydrogenation catalyst [RuH(cym)(L11)]BF 4 revealed restricted rotation about several of the P–C (ipso) bonds of the phosphorus substituents containing the 3,5-di-tert-butyl groups.The crystal structure of the latter complex revealed the cymene ligand not to be symmetrically bound to the ruthenium atom.25 The preparation of both diastereomeric derivatives of 3-(diphenylphosphanyl)pyrrolidine with chiral (tetrahydrofuran-2-yl)methyl and [(N-neopentyl)pyrrolidin-2-yl]- methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)-1- benzyl-4-(diphenylphosphanyl)-2-(methoxymethyl)pyrrolidine has been reported.[3S,P(RS)]-3-(Phenylphosphanyl)pyrrolidine, bearing an additional chiral center on 107 Nitrogen, phosphorus, arsenic, antimony and bismuthphosphorus, is the starting material for the preparation of phosphines, in which one phenyl group of the PPh 2 moiety is substituted by a 2-methoxyphenyl or 2,4,6- trimethoxyphenyl group.Palladium(II) iodide complexes of these ligands have been separated into diastereoisomers by chromatography on silica gel columns.The structural chemistry of these novel phosphane diastereomers and their PdI 2 complexes have also been investigated by X-ray crystallography and NMR studies.26 The organopalladium complex containing orthometallated (S)-[1- (dimethylamino)ethyl]naphthalene as the chiral auxiliary has been successfully used to promote the asymmetric [4]2] Diels–Alder reactions between 1-phenyl-3,4- dimethylphosphole and the following co-ordinated dienophiles: (a) diphenylvinylphosphine; (b) (E)-diphenylprop-1-enylphosphine; (c) (Z)-diphenylprop-1-enylphosphine.Reaction (a) generates three carbon and one phosphorus stereogenic centers while reactions (b) and (c) each produce four carbon and one phosphorus chiral centers. In dichloromethane, all three reactions proceeded smoothly at room temperature giving the corresponding rigid diphosphines in high yields.Under similar reaction conditions, the reaction times observed for reactions (a)–(c) are 2, 3 and 50 h, respectively. 2-D ROESY NMR studies confirmed that the prolonged reaction time required for reaction (c) is due to several major repulsive interactions between the chiral naphthylamine auxiliary and the (Z)-methyl-substituted vinylphosphine in the transition state.The absolute stereochemistries of the three bidentate phosphine ligands that were produced from the cycloaddition reactions have been assigned by 2-D ROESY NMR spectroscopy.27 An optically pure diphosphine ligand containing two phosphorus and four carbon stereogenic centres has been e¶ciently prepared by a chiral organopalladium complex promoted asymmetric Diels–Alder reaction between phenylbis[(Z)prop-1-enyl]phosphine and 1-phenyl-3,4-dimethylphosphole.28 The complexation and aggregation behavior of P,P@-di(2-ethylhexyl) ethanediphosphonic acid, H 2 DEH[EDP], a novel solvent extraction reagent for metal ions, has been investigated.The aggregation of H 2 DEH[EDP] was studied in toluene at 25 °C by vapor pressure osmometry.The acid was found to be hexameric in the concentration range 0.2–0.005M. Metal ions introduced into the organic phase were shown to have little e§ect on the aggregation of the extractant. Infrared spectroscopic studies of metal-containing solutions of the extractant and that of the ligand itself suggest that H 2 DEH[EDP] exists in toluene as a cyclic hexamer similar to an inverted micelle with a large hydrophilic cavity.Calcium(II), BaII, EuIII, FeIII, ThIV and UVI salts of H 2 DEH[EDP] were also investigated by infrared spectroscopy.29 4 Arsenic The structural features of complexes involving thioarsenic ligands bound to transition metal and main group elements have been described. Intermolecular associations are very common and have been discussed within the context of supramolecular chemistry. 30 The sodium-reduced form of the mixed trimer and tetramer of cyclo-methylarsathiane, cyclo-(CH 3 AsS) 3,4 , in thf reacts at room temperature with the metallocene dichlorides of Group 4 elements to give the metallacyclic complexes (g5- 108 K.K. Hii and T.P. KeeCp) 2 M(SCH 3 AsSCH 3 AsS) (M\Ti, Zr or Hf) and (g5-Cp*) 2 Zr(SCH 3 AsS).31 All four complexes are isomorphous, consisting of a cyclohexane-like six-membered MS 3 As 2 ring in a chair conformation with two g5-Cp rings on the metal atoms in pseudoequatorial and -axial positions and the methyl groups on arsenic in equatorial positions.These complexes have the same molecular structure as the all-sulfur metallacycles Cp 2 MS 5 (M\Ti, Zr or Hf).The complex containing Cp* groups forms a four-membered metallacycle similar to Cp* 2 TiS 3 . A series of amido derivatives of arsenic cyclopentadienyls (R@AsNR)n (R@\Cp*, R\H, n\4; R@\Cp*, R\Me; n\2, R@\C 5 Pr* 4 H, R\Me, n\2) has been synthesized by the reaction of R@AsX 2 (R@\Cp*, X\Cl; R@\C 5 Pr* 4 H, X\I) with an excess of amine. In the case of bulky amines, viz.NH2 Bu5 and NH(SiMe 3 ) 2 , monoamido substituted arsanes Cp*AsCl[(NRR2)R1] (R1\H, R2\Bu5; R1\R2\SiMe 3 ) have been obtained by treatment of Cp*AsX 2 with an excess of NH 2 Bu5 or with one equivalent of NaN(SiMe 3 ) 2 . The fluorine substituted analogue, Cp*AsF[N(SiMe 3 ) 2 ], has been synthesized in moderate yields. The complex Cp*AsX 2 reacts with strong bases to give diazadiarsetane (Cp*AsNBu5) 2 whereas reaction with Ph 2 C–– NNH 2 in the presence of NEt 3 as a base gives the disubstituted hydrazonato arsane Cp*As(NHN––CPh 2 ) 2 , independent of the reagent ratio.All new compounds have been characterized by standard spectroscopic methods and elemental analyses including single-crystal X-ray di§raction methods. Bonding of the arsenic fragment to the cyclopentadienyl ligand was described as a primary p interaction with an additional n interaction between the cyclopentadienyl ligand and the arsenic atom resulting in pseudo-g2 to g3-co-ordination.32 5 Antimony and bismuth The synthesis and structural characterisation of the first unco-ordinated phosphorussubstituted stibolyl anion containing the 2,4-diphosphastibolyl ring anion, [C 2 Bu5 2 P 2 Sb]~, has been described.33 The reaction of the hetero-ring anion [C 2 Bu5 2 P 2 Sb]~ with [MM(g4-1,5-C 8 H 12 )ClN2 ], M\Rh or Ir, leads to the formation of [M(g5-(C 2 Bu5 2 P 2 Sb)(g4-1,5-C 8 H 12 )],M\Rh or Ir.Treatment of CoCl 2 with either an equimolar mixture of [C 2 Bu5 2 P 2 Sb]~and [C 5 Me 5 ]~, or two equivalents of [C 2 Bu5 2 P 2 Sb]~ a§ords the compounds [Co(g5-C 5 Me 5 )(g4-C 2 Bu5 2 HP 2 Sb)] 8, and [Co(g5-C 2 Bu5 2 P 2 Sb)(g4-C 2 Bu5 2 HP 2 Sb)] 9, which represent the first examples of diphosphastibacyclopentadiene complexes.34 P Co P Sb H But But 8 Sb P P P Co P Sb H But But 9 But But The reaction between R 3 SbCl 2 (R\Me or Ph) and R@2 PO 2 Na (R@\Me or Ph) has been shown to a§ord R 3 Sb(O 2 PR@2 ) 2 derivatives which have been investigated by infrared and multinuclear NMR spectroscopy.Attempts to grow crystals of 109 Nitrogen, phosphorus, arsenic, antimony and bismuthMe 3 Sb(O 2 PPh 2 ) 2 led to colourless needles identified by X-ray di§raction as Me 3 Sb(OH)[O(O)PPh 2 ], produced presumably by partial hydrolysis. The co-ordination environment around the central metal atom was shown to be a distorted trigonal bipyramidal with carbon atoms of the SbMe 3 unit in equatorial positions and two oxygen atoms occupying the axial positions [O–Sb–O 175.7(1)°].The two antimony –oxygen distances are significantly di§erent [Sb–O(H) 1.967(3), Sb–O(P) 2.235(2)Å], as are the phosphorus–oxygen bond lengths in the basically monodentate diphenylphosphinato ligand [P–– O 1.528(3), P–– O 1.490(3)Å].The molecules are associated into polymeric chains through intermolecular hydrogen bonds between hydrogen of the hydroxo group and oxygen double bonded to phosphorus.35 Four Group 15 monochlorides of the type ER 2 Cl MR\2-(Me 2 NCH 2 )C 6 H 4 , E\Sb or Bi; R\8-(Me 2 N)C 10 H 6 , E\Sb or BiN have been prepared via the salt elimination reactions of two equivalents of either 2-(Me 2 NCH 2 )C 6 H 4 Li or 8- (Me 2 N)C 10 H 6 Li with ECl 3 . In addition, four related group 15 dihalides of the type ERX 2 [R\8-(Me 2 N)C 10 H 6 , X\Cl, E\As or Sb; R\2-(Me 2 NCH 2 )C 6 H 4 , X\Cl, E\Bi; X\I, E\Bi] have also been prepared via the salt elimination reactions of equimolar amounts of 8-(Me 2 N)C 10 H 6 Li or 2-(Me 2 NCH 2 )C 6 H 4 Li with EX 3 .Several single-crystal structures are described, and the observed trends in the degree of intra-molecular co-ordination of the nitrogen atoms are consistent with the view that the Lewis acidity of these complexes is associated with the E–X p* orbitals.36 Three cationic aryl–antimony and aryl–bismuth complexes stabilized by intra- or inter-molecular co-ordination have been prepared.Treatment of either SbR 2 Cl or BiR 2 Cl [R\2-(Me 2 NCH 2 )C 6 H 4 ] with TlPF 6 a§orded [SbR 2 ]PF 6 or [BiR 2 ]PF 6 , respectively.A related complex, [SbPh 2 ]PF 6 , stabilized by intermolecular co-ordination, was prepared via the reaction of SbPhCl 2 with two equivalents of TlPF 6 in the presence of an excess of OP(NMe 2 ) 3 . Crystal structure analyses revealed the coordination geometry at the Group 15 element centre in each new compound to be distorted trigonal bipyramidal.37 The syntheses and room-temperature single-crystal X-ray structural characterization of 1: 3 adducts formed between silver(I) pseudo-halides, AgX, and triphenylstibine, SbPh 3 have been described for X\Cl, I, SCN, NCS, CN or NO 3 . The chloride, as its methanol solvate, is isomorphous with the arsine analogue. A new form of the chloride has also been authenticated.No bromide has been obtained but the iodide is described. The thiocyanate crystallizes from acetonitrile or pyridine as an S-bonded form isomorphous with the arsine analogue. From 2-methylpyridine, remarkably, a solvate is obtained in which the thiocyanate is N-bonded. The unsolvated 1: 3 mononuclear nitrate complex [(Ph 3 Sb) 3 Ag(O 2 NO)]38 is isomorphous with the arsenic and phosphorus analogues.References 1 K.K. Hii and T. P. Kee, Annu. Rep. Progr. Chem., Sect. A, 1997, 93, 75. 2 K. Koga and K. Odashima, Yakugaku Zasshi, 1997, 117, 800. 3 V.V. Dunina, E. B. Golovan, N. S. Gulyukina, Y. K. Grishin and I. P. Beletskaya, Russ. Chem. Bull., 1997, 46, 1331. 4 A.L. Abuhijleh, J.Inorg. Biochem., 1997, 68, 167. 110 K.K. Hii and T.P. Kee5 A.D. Keramidas, S. M. Miller, O. P. Anderson and D. C. Crans, J. Am. Chem. Soc., 1997, 119, 8901. 6 T.X. Neenan, W. L. Driessen, J. G. Haasnoot and J. Reedijk, Inorg. Chim. Acta, 1997, 247, 43. 7 M. S. Driver and J. F. Hartwig, J. Am. Chem. Soc., 1997, 119, 8232. 8 R. Fernandez Galan, F. A. Jalon, B. R.Manzano, J. Rodriguez de la Fuente, M. Vrahami, B. Jedlicka, W. Weissensteiner and G. Jogl, Organometallics, 1997, 16, 3758. 9 J. Sletten and H. Grove, Acta. Chem. Scand., 1997, 51, 822. 10 J. Cano, G. DeMunno, J. L. Sanz, R. Ruiz, F. Lloret, J. Faus and M. Julve, An. Quim., 1997, 93, 174. 11 A. Vidal Ferran, A. Moyano, M. A. Pericas and A. Riera, J. Org. Chem., 1997, 62, 4970. 12 G.Hilmersson, P. I. Arvidsson, O. Davidsson and M. Hakansson, Organometallics, 1997, 16, 3352. 13 R. terHalle, A. Breheret, E. Schulz, C. Pinel and M. Lemaire, Tetrahedron: Asymmetry, 1997, 8, 2101. 14 J. L. Wesemann and M.H. Chisholm, Inorg. Chem., 1997, 36, 3258. 15 K. Schweiger, A. Kienast, B. Latte and H. Homborg, Z. Anorg. Allg. Chem., 1997, 623, 973. 16 E. Gallo, E. Solari, C.Floriani, A. Chiesi Villa and C. Rizzoli, Inorg. Chem., 1997, 36, 2178. 17 X. Q. Yan, R. J. Batchelor, F. W.B. Einstein, X. H. Zhang, R. Nagelkerke and D. Sutton, Inorg. Chem., 1997, 36, 1237. 18 B. Crociani, S. Antonaroli, M. Paci, F. DiBianca and L. Canovese, Organometallics, 1997, 16, 384. 19 A. Saitoh, T. Morimoto and K. Achiwa, Tetrahedron: Asymmetry, 1997, 8, 3567. 20 S. Selvaratnam, P. H. Leung, A. J. P. White and D. J. Williams, J. Organomet. Chem., 1997, 542, 61. 21 T. V. RajanBabu, T. A. Ayers, G. A. Halliday, K. K. You and J. C. Calabrese, J. Org. Chem., 1997, 62, 6012. 22 B. Faure, O. Pardigon and G. Buono, Tetrahedron, 1997, 53, 11 577. 23 R. J. Doyle, G. Salem and A. C. Willis, J. Chem. Soc., Dalton Trans., 1997, 2713. 24 A. Sudo and K. Saigo, J. Org. Chem., 1997, 62, 5508. 25 G. Trabesinger, A. Albinati, N. Feiken, R. W. Kunz, P. S. Pregosin and M. Tschoerner, J. Am. Chem. Soc., 1997, 119, 6315. 26 U. Nagel and H. G. Nedden, Chem. Ber., 1997, 130, 989. 27 B. H. Aw, T. S. A. Hor, S. Selvaratnam, K. F. Mok, A. J. P. White, D. J. Williams, N. H. Rees, W. McFarlane and P. H. Leung, Inorg. Chem., 1997, 36, 2138. 28 P. H. Leung, S. Selvaratnam, C. R. Cheng, K. F. Mok, N. H. Rees and W. McFarlane, Chem. Commun., 1997, 751. 29 A.W. Herlinger, R. Chiarizia, J. R. Ferraro, P. G. Rickert and E. P. Horwitz, Solvent Extr. Ion Exch., 1997, 15, 401. 30 I. Haiduc, Coord. Chem. Rev., 1997, 158, 325. 31 O.M. Kekia and A. L. Rheingold, Organometallics, 1997, 16, 5142. 32 E. V. Avtomonov, K. Megges, X. W. Li, J. Lorberth, S. Wocadlo, W. Massa, K. Harms, A. V. Churakov and J. A. K. Howard, J. Organomet. Chem., 1997, 544, 79. 33 M.D. Francis, D. E. Hibbs, M. B. Hursthouse, C. Jones and K. M.A. Malik, J. Organomet. Chem., 1997, 527, 291. 34 S. J. Black and C. Jones, J. Organomet. Chem., 1997, 534, 89. 35 C. Silvestru, A. Silvestru, I. Haiduc, D. B. Sowerby, K. H. Ebert and H. J. Breunig, Polyhedron, 1997, 16, 2643. 36 C. J. Carmalt, A. H. Cowley, R. D. Culp, R. A. Jones, S. Kamepalli and N. C. Norman, Inorg. Chem., 1997, 36, 2770. 37 C. J. Carmalt, D. Walsh, A. H. Cowley and N. C. Norman, Organometallics, 1997, 16, 3597. 38 E§endy, J. D. Kildea and A. H. White, Aust. J. Chem., 1997, 50, 587. 111 Nitrogen, phosphorus, arsenic, antimony and bismuth

ISSN:0260-1818    

DOI:10.1039/ic094099

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

8 Oxygen, sulfur, seleniumand tellurium By P. F. KELLY Department of Chemistry, Loughborough University, Loughborough LE11 3TU, UK 1 Introduction This review highlights new developments in the chemistry of the Group 16 elements (the chalcogens) reported during 1997. I have tried, as in other years, to emphasise results that demonstrate novelty of product or synthetic approach as their main feature.In addition, I have again tried to limit the products reported to those in possession of a discrete molecular structure, have generally avoided organo-chalcogen ligands such as alkoxides and have endeavouredto maintainwhat I feel to be a healthy disregard for results based on purely theoretical and/or computational considerations. 2 Sulfur, seleniumand tellurium The heavier chalcogens are renowned for their ability to combine with other p-block elements to formnew ring and cluster species.We begin by looking at such reactions, starting with elements in Group 13 and moving across. A new class of chalcogen substituted icosahedral boron cluster comes with selenoborates of the type [B 12 (BSe 3 ) 6 ]8~.1 The caesiumsalt of the latter forms when Cs 2 Se, boron and selenium are heated together (ratio 2: 9: 7) at 700°Cfor 2h.The product consists of the first B 12 icosohedron completely saturated with chalcogen ligands; in this case via trigonalplanar BSe 3 units linking to the central B 12 core. A smaller cluster unit of aluminium atoms is found in [Al 4 (H) 2 (NMe 3 ) 4 Se 5 ] which forms as the colourless product of the reaction of [MAl(NMe 3 )(H)(k-S)N2 ] with pentamethyldiethylenetriamine.2 A number of gallium–chalcogen systems have been investigated in the past year, including terminal selenides and tellurides of the type [Ga(E)TpB65,B65] which can be generated by oxidative addition of the elements to [GaTpB65,B65].3 In contrast to their indium analogues, the latter species can also be prepared using triethylphosphine chalcogenide as the chalcogen source.Larger gallium-based units include [MFe(CO) 2 CpNGa 4 E 4 ]4 (E\S, Se or Te) and the S-bridged cubane Mo–Ga clusters [Mo 3 Ga(H 2 O) 12 S 4 ]n` (n\5 or 6).5 While the former results from the reaction of [MFe(CO) 2 CpNGaCl 2 ] with E(SiMe 3 ) 2 , preparation of the latter involves direct reaction of elemental gallium with [Mo 3 (H 2 O) 9 S 4 ]4~ in HCl. Indium too has received attention, in particular for its ability to form interesting telluride species.Thus while isolated [In 2 Te 6 ]6~ anions 1 are found in K 6 [In 2 Te 6 ]·4en,6 the [In 2 Te 6 ]2~ ions in 113[M(en) 3 ][In 2 Te 6 ] form as polymeric chains generated from fused five-membered In 2 Te 3 rings.7 Both products form during solvothermal reactions in en. 6– 1 In Te In Te Te Te Te Te 2– 2 S S Si S S Si Cl S Cl S The ‘halfway house’ between known C 2 S 2 and unknown C 2 O 2 has now been detected in an Ar matrix.8 When CS was mixed with CO on a CsI window at 10K and irradiated at 254 nm, new IR bands associated with C 2 SO appeared. This photochemically induced addition is, apparently, reversible. A six-membered Si 2 S 4 ring is present in the [Si 2 S 6 Cl 2 ]2~ anion 2 which forms when sodium sulfide reacts with [PPh 4 ]Cl and SiCl 4 in CH 2 Cl 2 .9 The silicon atoms, each bearing a chloride and a terminal sulfur, occupy the 1,4 positions; the same work also noted the formation of the 1,3 Psubstituted ring, [P 2 S 8 ]2~.As one might suspect, the silene Bu5 2 SiSiBu5 2 is reactive towards selenium and tellurium species.10 Thus selenophene reacts to produce a 1,3-diselena-2,4-disiletane, [Bu5 2 SiSe] 2 which has a planar four-membered Se 2 Si 2 ring.The analogous tellurium species has also been reported and indeed may be isolated in greater yield (63% compared to 11% for the selenium). Rather similar four-membered Sn 2 Se 2 rings are present in [MNi(PPh 3 )CpN2 Cl 2 Se 2 Sn 2 ], which forms when the reaction of [MNi(PPh 3 )CpNCl 3 Sn] with Se(SiMe 3 ) 2 is stopped after 16 h,11 and in the [Sn 2 Te 6 ]4~ anion Mfound in [Zn(N 2 C 2 H 8 ) 3 ] 2 [Sn 2 Te 6 ], formed when K 4 SnTe 4 alloy is treated with ZnCl 2 and [NEt 4 ]BrN.12 Tin is also a vital component of the first quaternary Zintl anion namely [Au(Ag 1~xAux) 2 Sn 2 Te 9 ]4~.13 This black crystalline material forms (as the [NEt 4 ]` salt) as black crystals after an en extract of K 6 Ag 2 AuSn 2 Te 9 alloy is treated with the cation and left for a number of months.It exhibits a 1-D chain structure; a combination of magnetic susceptibility, conductivity and optical measurements show it to exist in a Pierls distorted state and to display semiconducting, diamagnetic behaviour.Chalcogen–nitrogen systems continue to be an extremely fertile ground for new work. The smallest such unit, the NS ligand, has been shown to be capable of an unexpected oxo transfer reaction wherein a ruthenium intermediate bearing NS and nitrito ligands actually rearranges to end up with NSO and NO.14 A more well known rearrangement, that of S 2 N 2 to (SN)x, has now been studied by time-resolved X-ray powder di§raction leading to the conclusion that the polymerisation is of a nondi §usive nature involving a martensitic transition.15 The hope that a similar preparation of (SeN)x may one day be feasible has been given a boost by the realisation that complexes of the Se 2 N 2 ring ligand form from unexpected sources such as Se(NSO) 2 .16 A four-membered Te 2 N 2 ring is found in [Te 3 N 2 Cl 5 (SbCl 5 )]` 3 (from the reaction of Te 2 NCl 5 with SbCl 5 in CH 2 Cl 2 ),17 while larger rings are seen in five-membered Ph 3 SbS 2 N 2 (from Ph 3 Sb and S 3 N 2 Cl 2 ),18 [Se 3 N 2 Cl][SbCl 6 ] (the red crystalline product of the reaction of Se 2 NCl 5 with SbCl 3 )19 and in six-membered SeS 3 N 2 .20 The latter, analogous to long-known S 4 N 2 , forms in the reaction of a S 2 Cl 2 –Se 2 Cl 2 –SeCl 4 mix with [M(Me 3 Si) 2 NN2 S]; no examples of congeners with a higher selenium content could be generated. 114 P.F. KellyTe N Te N Cl3Te SbCl5 Cl Cl + 3 The carbon-containing dithiazolyl rings continue to provoke keen interest. While, on the face of it, there would appear to be relatively trivial structural di§erences between the 2,3 and 2,5 isomers of C 6 H 3 F 2 CNSNS, they lead to large changes in the solid-state structures.Though the former generates discrete twisted dimers, the latter exhibits uniform stacks with long (3.5Å) S · · · S contacts.21 This year also saw the first report of a protonated dithiazolyl in the form of the SNC(Ph)N(H)S ligand which bridges two palladium atoms in [Pd 2Mk-S 2 NN(H)C(Ph)N(dppe) 2 ][BF 4 ] 2 .22 The presence of the hydrogen on the metallacycle was confirmed through the changes in bond distances and angles within the latter and through a hydrogen-bonding e§ect towards the [BF 4 ]~ counter ion. A much larger, 16-membered, C–N–S ring comes in the form of (4-BrC 6 H 4 ) 4 C 4 N 8 Ph 4 .This forms during the reaction of 4-BrC 6 H 4 CN 2 (SiMe 3 ) 3 with PhSCl at low temperatures and exhibits a cradle-like structure with the four nitrogen atoms forming a square with edges of 3.07Å.23 The authors in this case speculate that this provides su¶cient room to accommodate a metal ion such as K`.Finally, in the area of S–N rings, the phosphorus system Et 4 P 2 N 4 S 2 Cl 2 has been reported to form when Et 4 P 2 N 4 S 2 reacts with SO 2 Cl 2 ; treatment with AlCl 3 generates [Et 4 P 2 N 4 S 2 Cl 2 ][AlCl 4 ] 2 .24 The reaction of Me 3 SiNPEt 3 and S 2 Cl 2 generates the non-cyclic S–N–P systems [S(NPEt 3 ) 3 ]` and [S(NPEt 3 ) 2 ]2` depending upon the exact ratios used.25 A variety of studies on the use of NSF-based ligands have been reported with perhaps the most interesting of the resulting complexes being [MNi(NSF 2 NMe 2 ) 3N2 (k- NSF 2 NMe 2 )]4` and [CoMNSF 2 NS(O)F 2N4 ]2`.The key feature of the former26 is the unprecedented appearance of a bridging N–– – S unit while the latter, uniquely, exhibits single, double and triple S–N bonds within the one ligand.27 When written as [N–– – SF 2 –N––S(O)F 2 ] this ligand shows S–Nlengths (from left to right) of 1.39, 1.59 and 1.50Å, confirming the three bond orders.Other systems noted include [Re(CO) 5 (NSX)]` (where X\F, Cl or Br),28 [Fe(CO) 2 (NSF 3 )Cp]` Mfrom [Fe(CO) 2 (SO 2 )Cp]` and NSF 3N29 and main group di(fluorosulfonyl)amides such as [Ph 3 PbN(SO 2 F) 2 ].30 A quite di§erent S–N ligand, Ph 2 SNH is present in [CuCl 2 (Ph 2 SNH) 2 ] which, unusually for a neutral CuII complex, exhibits squareplaner/ pseudo-tetrahedral isomerism.31 The basic concept of the reaction of white phosphorus with elemental sulfur has been appraised in a study which reveals that at temperatures of\100 °C twelve of the seventeen known binary phosphorus sulfides form (as revealed by 31P NMR spectroscopy). 32 Similar reactions occur at 0 °C via photoinitiation with visible light; in both cases the major product is a-P 4 S 7 (with the rate-determining step apparently being the formation of the S 8 diradical).The carbolic acid substitution reactions of a-P 4 S 3 I 2 33 and the iodination of arsenic-substituted species of the type AsnP 4~nS 3 34 have both been studied in depth as has the use of Ph 3 AsS and Ph 3 SbS as sulfur sources in reactions with phosphorus sulfides.35 The preparation of P 4 O 7 Se through photochemical selenation of P 4 O 7 has been reported; in this case the product possesses a terminal P–Se unit.36 Far greater amounts of selenium end up in the products formed 115 Oxygen, sulfur, selenium and telluriumwhen polyselenophosphate fluxes react at high temperatures with elemental metals.Thus gold is seen to produce 1-D chain anions of the type [AuP 2 Se 8 ]3~ 37 while cadmium or mercury give [M 4 (Se 2 ) 2 (PSe 4 ) 4 ]8~ 4.The complicated structures of the latter are based around stellane-like [M 4 (Se 2 ) 2 ]4` cores .38 P Se Se Se Se M Se M Se P Se Se Se M Se M P Se Se Se Se Se Se Se Se P Se Se 8– 4 Te Te Te Te Te Te Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se 6 5 2+ 2+ Te Te Heavier Group 15 elements can also get involved in cluster formation with chalcogens. Thus we see the [As 2 Te 4 ]4~ anion within the red crystalline product of the en extraction of Rb 4 As 2 Te 4 alloy.39 In addition, the thermal reaction of Rb 2 CO 3 with As 2 Se 3 and selenium in methanol results in the tetrahedral [AsSe 4 ]3~ anion40 while the antimony analogue of the latter acts as both bridging and terminal ligands in [Mn(en) 3 ] 2 [Mn 4 (en) 9 (SbSe 4 ) 4 ] (formed in the direct reaction of Mn, Sb and Se in en).41 Reaction of BiCl 3 with Te–TeCl 4 mixtures does not, however, generate Bi–Te products; rather, salts of the well known [Te 4 ]2` cation form.42 The latter is a good example of a ‘pure Group 16’ species; other recent examples include [Te 8 ]2` 5 and [Se 17 ]2` 6.The first of these forms in the solid-state reaction of ReCl 5 with a Te–TeCl 4 mix and is isostructural with [S 8 ]2` and [Se 8 ]2` (though the transannular bond present is shorter relative to its annular counterparts than is the case for S and Se congeners).43 The selenium ion is produced in the reaction of the element with SeCl 4 and NbCl 5 (150 °C) and consists of two Se 7 rings linked by a Se 3 chain.44 The cation/pH dependency of the speciation of polyselenides in water has been thoroughly investigated by electrospray mass spectrometry.45 Results indicate that it is possible to direct the major polyselenide species in water using these variables.Thus while sodium tetraselenide shows many Sen 2~ and HSen 2~ species in neutral/basic solutions, the potassium analogue has the dominant [Se 4 ]2~·H 2 O species.The first example of a stable derivative of [Te 3 ]4~, namely [(mes) 5 Te 3 ]` has been isolated.46 The latter consists of a three-membered Te ring, with a central (mes)Te bridge linking two terminal (mes) 2 Te units. Tellurium-125 NMR studies have shown that there is dynamic exchange in the system as well as fast exchange with excess (mes) 2 Te, prompting a parallel with the I 2 /I~][I 3 ]~ system.Of the sulfur oxides, SO 2 has been shown to react with CsF under ultrasound treatment (giving Cs 2 [S 3 O 6 ] and SO 2 F 2 )47 and, as a ligand, to undergo rapid migration over the metal atoms in the cluster core of [Ru 6 C(CO) 14 (SO 2 )(k-C 3 H 5 )]~.48 In the case of SO 3 , a combination of mass spectrometry and calculation has shown that solvation by twelve water molecules will allow it to be converted into sulfuric acid with little or no energy barrier.49 Finally, it is well worth noting that the ability of Cp 2 Ti units to insert into S–S bonds and then act as sources of new species has been demonstrated yet again.50 In this case cyclic organosulfanes are the starting materials; thus cyclo-S 2 (CH 2 S) 2 CH 2 reacts with [Ti(CO) 2 Cp 2 ] to give [TiMS 2 (CH 2 S) 2 - 116 P.F. KellyCH 2NCp 2 ] which in turn reacts with SCl 2 to liberate cyclo-S 3 (CH 2 S) 2 CH 2 .The same work also notes that S 6 reacts with carbonyl species to give a mixture from which [TiS 8 Cp 2 ] may be crystallised and treated with C 6 H 4 (SCl) 2 to give C 6 H 4 S 10 .Of chalcogen–halogen systems noted last year, the TeBr 2 ligand has been characterised for the first time Mbound to each rhenium atom in [Re 6 Te 8 (TeI 2 ) 6 ]2`N51 while its selenium analogue was shown to be present in [PdBr 2 (SeBr 2 ) 2 ] (which forms when the three elements are mixed in CCl 4 at 180 °C).52 The related [Te 2 I 6 ]2~ unit binds to niobium in [Nb 2 (k-Se 2 ) 2 (Te 2 I 6 ) 2 ]53 while gas electron di§raction data for TeCl 4 have presented a structure consistent with the VSEPR model (with average bonds of Te–Cl!9 2.435, Te–Cl%2 2.294Å).54 Halogen bridges result in extended structures for tellurium species of the type [TeXMe 2MS 2 CN(CH 2 )nCH 2N].55 Ir S S S S S S S S S S S S S S S S Te Te Te Te (CO)5Cr Cr(CO)5 Cr(CO)5 Cr(CO)5 7 3– 8 As usual a vast range of metal complexes containing chalcogenide ligands resulted from work published last year.Two that deserved special note come in the form of [Cr 4 (CO) 20 Te 4 ] 7 and [Ir(S 4 )(S 6 ) 2 ]3~ 8. In the first each, atom of a Te 4 ring coordinates to a Cr(CO) 5 unit; given that this ring is neutral, it follows that the complex can be meaningfully described as the first organometallic derivative of a Te allotrope. 56 It forms when [Nb(Te 2 H)Cp* 2 ] is treated with [Cr(CO) 5 thf] in the dark at room temperature and exhibits an average Te–Te length of 2.86Å. The aforementioned niobium starting material is itself interesting in that it contains the novel g2-Te 2 H ligand; NMR spectroscopy results suggest that the latter undergoes rapid H migration between the two tellurium atoms.The iridium compound results from the reaction of IrCl 3 ·nH 2 O with [NH 4 ] 2 [Sx] in water, a reaction which was first reported in 1904 when the product was formulated as [NH 4 ] 3 [IrS 15 ].57 The fact that they got the formulation so close is testimony to the excellence of the original work (by Hofmann and Hochtlen) and also provides a tantalising subtext.As the material in question resolved spontaneously upon crystallisation, it meant that enantiomeric crystals were available to the original workers a decade before Werner first separated optically active inorganic complexes. Terminal chalcogenide ligands are found in two di§erent types of vanadium species: the sulfide and selenide complexes [V(Ndmpad) 3 E] (which form as burgundy-red crystalline materials)58 and in the first structurally characterised terminal telluride complex of this metal (in this case, supported by anN 4 macrocycle).59 Disulfur bridges link the niobium atoms in [Nb 2 (H 2 O) 8 (k-S 2 ) 2 ]4` (which happens to be the first structurally characterised aqua–NbIV complex),60 while an [S 4 ]2~ chain links the platinum dimers in [Pt 4 Cl 2 (5-mpyt) 8 (k-S 4 )]61 and a very rare example of a M 2 (k,g2- S 2 ) 2 bridge occurs in [M 2 (tpp) 2 (S 2 ) 2 ] (M\Zr or Hf).62 Trinuclear [MoAu 2 (AsPh 3 ) 2 S 4 ] results from the reaction of [MoS 4 ]2~ with HAuCl 4 and AsPh 3 ,63 while clusters of the type [MonW 3~n(CO) 6 (k3 -P)Cp 3 ] can be reversibly 117 Oxygen, sulfur, selenium and telluriumoxidised by sulfur to give k3 -PS complexes.64 Three metal atoms are also present in [M 3 (CN) 9 Se 4 ]5~ (M\Mo or W),65 in [Mo 3 (H 2 O) 6 E 7 ]4` (where E is S or Se and from which three equivalents of chalcogen may be abstracted with phosphines)66 and in [Fe 3 (CO) 9 Te 4 (CTeBr 4 )] Mfrom the reaction of [Fe 3 (CO) 9 Te 2 ] with CBr 4N.67 S S S S Cu S S S S S Cu S Mo S S Cu S S 3- 9 Among the tetranuclear clusters reported in 1997 are [MoCu 3 S 4 (S 5 ) 2 ]3~ 9,68 [W 4 (PMe 2 Ph) 4 (k-S) 6 ] Mthe purple product of the reduction of [W 4 Cl 2 (PMe 2 Ph) 4 (k- S) 6 ] with sodium amalgamN,69 [(TiCp) 4 (k3 -S) 3 (k2 -S)(k2 -SEt) 2 ] (from the thermolysis of [TiMeCl 2 Cp], ethanethiol and a base)70 and [Mn 4 (CO) 13 (Te 2 ) 3 ]2~ Mthe product of the sealed-tube reaction of [Mn 2 (CO) 10 ], Na 2 Te and [PPh 4 ]Br in ethanolN,71 while pentanuclear [Fe 5 S 12MMe 2 Si(g5-C 5 H 4 ) 2N2 ] forms from sulfur and [Fe 2 (CO) 4MMe 2 Si(g5-C 5 H 4 ) 2N2 ] in refluxing toluene.72 Hexanuclear systems reported include mixed Te–Se Re 6 clusters of the type [Re 6 (CN) 6 (Te 8~nSen)] (where n\0 to 8),73 a range of tungsten clusters of formula [W 6 Te 8 L 6 ] (with L being an amine or PEt 3 ),74 the first examples of clusters containing the face-capped octahedral [Re 6 (k3 - E) 8 ]2` Mincluding among them [Re 6 Se 7 (SeH)I 6 ]3~, for exampleN75 and [Mo 6 Se 42 ]6~ Mthe black crystalline product of the thermal reaction of Mo(CO) 6 , Ag, K 2 Se 4 and [NEt 4 ]Cl in ethanolN.76 Larger clusters include [Cu 7 As 3 Te 13 ]4~ (based around a cubane-like MCu 7 TeN core),77 [Re 12 (MeCN) 2 (PEt 3 ) 8 Se 16 ]4` (constructed of two individual cluster units bridged by a Re 2 Se 2 rhomb),78 [MW 2 Ag 2 S 2 O 2 (S 2 C 2 H 4 ) 2N3 (k-S 6 )2~] (the first dodecanuclear M–Ag–S cage cluster)79 and the super-large [Cu 59 (PCy 3 ) 15 Se 30 ].80 The latter forms in the condition-dependent addition of the phosphine to copper(I) acetate and Se(SiMe 3 ) 2 ; changing the precise conditions results in clusters with a smaller Cu content.On the general subject of Group 16 metal clusters, a 104 reference review of the solvothermal synthesis of solid-state chalcogenidometalates is most worthy of note.81 Finally, the range of cluster species that result from reaction of copper sulfides with white phosphorus82 and from laser ablation of manganese sul- fide83 have been studied by FT ion cyclotron resonance mass spectrometry and, in the latter case, reconciled with structural calculations.84 3 Oxygen As with previous years many new oxidation systems for alkanes, alkenes, etc.have been reported. For example fluorous biphasic catalysis of the functionalisation of a range of alkanes and alkenes by O 2 and Bu5O 2 H has been noted, with e¶cient separation of the products and the catalysts between the two phases,85 while lithiumdoped sulfated zirconia catalysts e§ect the oxidative coupling of methane (and are the first examples of solid super-acid based materials to do this).86 The low-temperature oxygenation of methane to formic acid is catalysed by 118 P.F.Kelly[Pd 0.08 Cs 2.5 H 1.34 PVMo 11 O 40 ]87 while dioxygen in air can oxidise isobutane to tert-butyl alcohol if the former is in the supercritical phase on a SiO 2 /TiO 2 or Pd–C catalyst.88 The osmium species [Os(CN) 2 (dpphen)O 2 ], which is made by reaction of dpphen, K 2 [Os(CN) 2 (OH) 2 O 2 ] and [NBu 4 ]Cl, and which exhibits trans oxo groups, has been shown to be the first example of a well defined metal oxo complex capable of oxidising the unreactive C–Hbonds of saturated hydrocarbons such as cyclohexane.89 Thus, under UV/VIS irradiation, in the presence of air, oxidation of the aforementioned alkane became catalytic with a turnover of 16 after 12 h.In such reactions the product consists of a mixture of ketones, aldehydes and alcohols. It has been demonstrated that [Mn 2 (phen) 4 (k-O) 2 ]3` can oxidise hydrocarbons via hydrogen abstraction (and subsequent k-OH complex formation) and thus transforms 9,10-dihydroanthracene into anthracene, for example.90 Another binuclear manganese complex, [Mn 2 L 2 (k-O) 3 ] (L\1,4,7-trimethyl-1,4,7-triazacyclononane), proves to be an excellent catalyst for the selective and fast conversion of substituted benzyl alcohols to benzaldehydes using either H 2 O 2 or tert-butylhydroperoxide.91 In a related area, reduction of NO to N 2 by hydrocarbons in the presence of excess O 2 has been investigated using the ‘intermediate addition of reductant’ method.92 Finally, unlike most other Co porphyrins, cobalt porphine, adsorbed on graphite electrodes, has been shown to catalyse the direct reduction of O 2 to water,93 while H 2 O 2 reacts with rutile TiO 2 powder to generate triplet radical anion pairs of two interacting O~· ··O~ centres.94 The latter occupy very specific sites (some 5.9Åapart) and are not observed to form on anatase TiO 2 .The first syntheses of fluorocarbonyl- and trifluoracetyl-peroxynitrate derivatives have been reported. Both are low boiling colourless liquids; the former [FC(O)OONO 2 ] results from the photolysis of a mixture of (FCO) 2 , NO 2 and O 2 ,95 while the latter forms when the product of the reaction of [CF 3 C(O)] 2 O with H 2 O 2 is treated with HNO 3 –H 2 SO 4 (acting as a source of [NO 2 ]`).96 General interest in peroxynitrate stems from its potential relevance to the toxicological e§ects of NO 2 in smog (it is the possible product of the reaction of superoxide with NO 2 in the lungs).97 The ability of a related anion, peroxynitrite, to react with CO 2 to give toxic [ONOOCO 2 ]~ has also been noted,98 as has its slow reduction by sulfite at high pH in the presence of a CuII catalyst.99 Nitrosyl thiocyanate, ONSCN, reacts with the thiocyanate anion to give the [ON(SCN) 2 ]~ adduct which is crucially not the same as the product formed whenNOreacts with (SCN) 2 ~ (with the key di§erence being that it is an S-nitroso species as opposed to N-nitroso).100 Finally among Group 15 oxygen species, it should be noted that P 4 O 8 has been made in pure form for the first time by treating P 4 O 9 with red phosphorus at 430 °C for 1 d followed by toluene extraction.101 The soluble P 4 O 8 is removed from the system leaving insoluble starting material behind.As expected it consists of a P 4 O 6 cage with two terminal P–O bonds. In addition to the sulfur–oxygen species mentioned earlier, the photochemical isomerism (S-bound to O-bound) of the sulfito ligand in a CoIII complex has been investigated,102 and calculations have been performed that model the oxidation of [HSO 3 ]~ to sulfuric acid by hydrogen peroxide.103 The results suggest that under acid conditions SO 2 and not [HSO 3 ]~ is the reactive species, a conclusion that has relevance to the modelling of the formation of acid rain.The red crystalline material that forms from solutions of RhCl 3 and 1,6-diammoniohexane dichloride has been shown to be [H 3 N(CH 2 ) 6 NH 3 ] 2 [H 9 O 4 ][RhCl 6 ]Cl 2 .104 It exhibits cavities within the 119 Oxygen, sulfur, selenium and telluriumresulting organic/inorganic matrix wherein lie [H 9 O 4 ]` cations.The latter may be best described as a [H 5 O 2 ]` cation with additional water molecules at each side, H-bonded via O lone pairs. As such it constitutes the first example of the cation in the solid state existing as a distinct structural unit (as opposed to the further hydrogen bonded [H 18 O 8 ]2`).The singlet oxygen production e¶ciency of several laser-excited fullerene derivatives has been the subject of an investigation,105 whilst the gas itself has been shown to react with Pd and Ni mercaptoethyl derivatives to produce isolable metallasulfones and sulfoxides.106 I O I O O O2+ 10 Halogen–oxo species continue to generate much interest. For example, in contrast to previous suggestions, the crystal structure of the [(IO 2 ) 2 ]2` cation 10 in [IO 2 ] 2 [S 2 O 7 ] (crystallised from the I 2 O 5 –SO 3 –H 2 Osystem) reveals it to be dimeric with two terminal and two bridging oxygens.107 Interestingly, interaction from iodine to the anion results in the formation of chain-like polymeric strands, while the bonds within the cation itself show a surprising degree of asymmetry.108 Unexpected results are also seen for another I–O system: HIO 4 .In this case a combination of X-ray- and neutrondi §raction has revealed 1-D infinite chains made up of distorted, cis edge sharing IO 6 octahedra, with each chain connected to four adjacent chains through H-bonds.109 The related species iodine superoxide, [IOO]·, has been isolated on a CsI window at 12K after flash pyrolysis of an iodine–oxygen mix in argon.110 Its proves to be less stable than the other halogen analogues and forms iodine dioxide upon irradiation at 254 nm.The IR spectrum of the latter suggests a bent structure with the I–O bonds possessing some double bond character.Finally, amongst iodine systems, the formation of cyanoiodine dinitrate from ICN and excess ClONO 2 has been reported, with the product being characterised by vibrational spectroscopy.111 A number of bromine–oxo species were reported in 1997, among them BrONO which forms when its matrix-isolated isomer BrNO 2 (itself generated from ClNO 2 using aqueous bromide) is irradiated with visible light.112 Related bromine nitrate, BrONO 2 , has been characterised by X-ray crystallography (revealing intermolecular Br .. .O interactions which result in chain formation)113 while a novel synthesis (via hydrolysis of BrOTeF 5 ) and single-crystal determination of Br 2 O has been undertaken. 114 The molecule is confirmed as bent (114.2°) with long range Br .. .Br contacts generating a chain array. The chloro compound ClOSF 5 results from the action of ClF upon SOF 2 in the presence of activated CsF; electron di§raction and a combination of IR and Raman spectroscopy confirms the expected octahedral geometry about the sulfur, with an S–O–Cl angle of 119.2°.115 Moving on to fluorine, the first experimental characterisation of the pre-reactive complex in the F 2 –H 2 O system has been performed. 116 Using a fast-mixing nozzle technique it can be shown that supersonicH 2 O and F 2 form H 2 O · · · F 2 in three-body collisions within 1 ks of mixing. Microwave spectroscopy suggests an O· · ·F interaction of 2.72Å. Finally on the subject of halogen oxides, it is worth noting a 67 reference review on the solid-state structural chemistry of binary halogen oxides.117 As is usually the case, many examples of transition-metal oxo complexes were 120 P.F.Kellyreported last year; here we note just a few. Electrospray tandem mass spectrometry has been used to demonstrate that discrete MnV complexes with terminal oxo groups act as oxygen sources during [Mn(salen)]` catalysed epoxidations.118 Similar terminal groups are found in [MoCl 3 (EtOH)O] (obtained as green crystals from the ethanolysis of MoCl 5 )119 and in [ReO(S 2 NCCF 3 ) 2 ]~, which forms when [ReS 4 ]~ is treated with CF 3 CN in the presence of an O-donor.120 A combination of bridging and terminal oxygens is seen in alkylrhenium(VI) oxides of the type [ReRR@(O)(k-O)] 2 ,121 while the larger superoxo unit is found in [Co(CN) 4 (B)(O 2 )]2~ (where B is a base such as pyridine).122 The latter form when [NBu 4 ] 2 [Co(CN) 4 (B)] reacts withO 2 ; the presence of the large cation mitigates against the formation of bridging peroxo products, making the reaction reversible and allowing repeated oxygen cycling.Peroxo systems studied recently include the products of the oxygenation of a range of biomimetic CuI receptors based upon crown ether derivatives123 and the first examples of fullyformed, stable, copper–dioxygen complexes.124 In the latter, the entropic destabilisation of k-peroxo-dicopper units is overcome by the nature of the other ligands present (binucleating pyridine-based multidentate species) and of the solvent (acetone).Methylrhenium diperoxide has been shown to decompose to perrhenic acid along solvent-dependant pathways.125 Thus while methanol and hydrogen peroxide are formed in water, the light-facilitated decomposition in acetonitrile generates CH 3 OOH.As an aside to this result it is noteworthy that a new economical and simple route to alkylrhenium oxides from perrhenates (via treatment with Me 3 SiCl and SnMe 4 ) has been reported.126 Detailed mechanistic studies upon the reaction of [FeII(edta)]2~ with O 2 have identified four steps: formation of [Fe(edta)O 2 ]2~; electron transfer to give an FeIII superoxo species; generation of [MFeIII(edta)N2 (k-O 2 )]4~; and finally a fast decomposition to [Fe(edta)]~ andH 2 O 2 .127 In contrast, the primary products in the reaction of a number of CuI complexes of 1-azadiene chelates with O 2 could not be determined, though ultimate products based upon dimeric CuII structures linked by bridging OH groups were characterised.128 Finally, the customary plethora of oxo cluster compounds were noted, including [Eu 8 (dmf) 13 (k4 -O)(k3 - OH) 12 (Se 3 )(Se 4 ) 4 (Se 5 ) 2 ] (as red plates from K 2 Se 4 and EuCl 3 in dmf),129 [Mn 10 O 8 (O 2 CPh) 6 (pyca) 8 ]130 and the product of the reaction of 1,3-dimethyl-2- iminoimidazoline with LiMe.131 The latter exhibits a [Li 12 Cl 2 N 8 O 2 ] core composed of a stack of ladder fragments incorporating a peroxo unit.References 1 J. 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Fischer, Angew. Chem., Int. Ed. Engl., 1997, 36, 2652. 127 S. Seibig and R. van Eldik, Inorg. Chem., 1997, 36, 4115. 128 D. Walther, K. Hamza, H. Gorls and W. Imhof, Z. Anorg. Allg. Chem., 1997, 623, 1135. 123 Oxygen, sulfur, selenium and tellurium129 C. G. Pernin and J. A. Ibers, Inorg. Chem., 1997, 36, 3802. 130 H. J. Eppley, S. M. J. Aubin, W. E. Streib, J. C. Bollinger, D. N. Hendrickson and G. Christou, Inorg. Chem., 1997, 36, 109. 131 N. Kuhn, U. Abram, G. Maichle-Mossner and J. Wietho§, Z. Anorg. Allg. Chem., 1997, 623, 1121. 124 P.F. Kelly

ISSN:0260-1818    

DOI:10.1039/ic094113

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

9 Halogens and noble gases By E.G. HOPE Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK 1 Introduction This chapter reviews the 1997 literature for the elemental halogens and the noble gases and compounds containing these elements in their positive oxidation states only. Publications which involve halide or oxohalide anions as counter ions are not described. 2 Halogens In the first high-resolution threshold photoelectron spectroscopic study of molecular fluorine across the full valence ionization region, in addition to the familiar three-band system for F 2 `, extensive structure in the Franck–Condon gap region between the ionic states is observed which arises fromresonance autoionization involving Ryberg states lying in these regions.1 Ab initio calculations on the molecular packing of crystalline Cl 2 led to the conclusion that it is not a normal van der Waals solid.2 In recent years, control of the extreme reactivity of fluorine has been achieved in several ways that have made it a useful reagent for performing a wide range of reactions in both inorganic and organic chemistry.Examples this year include the use of fluorine: (i) in diluted flow systems, e.g.the exhaustive fluorination of bicyclic systems3 and the synthesis of a series of mono- and bis-N-fluoro compounds,4 (ii) in solution, e.g. in aqueous solution for the in situ oxidation of ketones or in the generation of secondary ketones or a-hydroxyketones by direct reaction with anhydrous alcohols or 1,2-diols5 and in anhydrous HFfor the low-temperature oxidation of goldmetal yielding, in this instance, Au(SbF 6 ) 2 Au(AuF 4 ) 2 ,6 (iii) in the gas phase, e.g.in the modification of carbon fibre surfaces,7 for the generation of fluorine–graphite intercalationcompounds,8 and in the synthesis of crystalline, binary and ternary metal fluorides under high pressure–high temperature conditions.9 Electrophilic fluorination, a formal F`transfer event, has also been receiving attention, particularly with the commercial availability of reagents such as SelectFluor'; see for example the first applicationof SelectFluor' in carbohydrate chemistry10 andthe reactionof F-TEDABF 4 M1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2·2·2]octane bis(tetrafluoroborate) N with b-ketosulfoxides.11 However, there is controversy about the mechanismof fluorination arising from the homolytic and heterolytic F–F bond dissociation ener- 125gies and it has been suggested that F 2 ·` is a more reasonable fluorine source.The F 2 ·` ion has now been generated in the external source of a Fourier-transform ion cyclotron resonance mass spectrometer and has been allowed to react with noble gases (see below) and polyatomic molecules permitting the experimental derivation of the proton a¶nity of fluorine (79^5 kcal mol~1).12 Chlorination of C 60 13 and bromination of C 70 14 yield C 60 Cl 24 and C 70 Br 14 respectively.Chlorination of Fe(CO) 5 in SbF 5 under a CO atmosphere gives the homoleptic iron carbonyl cation [Fe(CO) 6 ]2`.15 This completes the series of these derivatives in the iron triad.In an interesting twist, following the report of iodination using elemental fluorine as a co-oxidant, iodine has been used as an oxidant in a convenient synthesis of SnF 4 from SnF 2 16 and in the formation of P–F bonds by desulfurization of phosphorothiolate and phosphorodithiolate diesters in the presence of triethylamine–tris(hydrofluoride).17 The hydrate of bromine, Br 2 ·10H 2 O, one of the first clathrate hydrates to be discovered, has been extensively studied but its detailed structure has only now been established for the first time.18 Sixteen di§erent crystals of distinct compositions (Br 2 ·8.62H 2 O to Br 2 ·10.68H 2 O) and morphologies show that there is just a single, tetragonal, structure as proposed in 1963.Charge-transfer complexes of the halogens and donor molecules continue to produce a fertile area for research.Bromine–alkene 1: 1 n-complexes are the first, and usually short lived, intermediates in electrophilic bromination. The first evidence, from UV/VIS spectroscopy, of a 2: 1 bromine–alkene complex formed in the bromination of tetraneopentylethene has been reported.19 The reaction of 2,3,5,6-tetrakis(2-pyridyl) pyrazine with iodine gives 1: 1 and 1: 2 adducts.20 In the structurally characterised 1: 2 adduct, the inversion-related pyridyl rings and the I 2 units condense into distinct channels in the three-dimensional array (Fig. 1). The solid-state and solution structures in the triphenylphosphine–iodine system have been studied in detail. At a 1: 1 ratio, a molecular adduct, the charge-transfer complex [Ph 3 PI]`I~, exists in solution and at higher ratios the adduct dissociates into [Ph 3 PI]`and I 3 ~ or I 5 ~ depending on the molar excess of iodine.21 Diiodine charge-transfer complexes of thioether crowns ([9]aneS 3 , [12]aneS 4 , [14]aneS 4 or [16]aneS 4 ) exhibit a range of di§erent assemblies in the solid state but the 1: 1 adducts are the predominant species in solution.22 In the crystal structures of adducts with a new 1: 4 stoichiometry, [16]aneS 4 ·4I 2 22 and [14]aneS 4 ·4I 2 ,23 all four sulfur atoms are involved in linear S–I–I charge-transfer interactions, with intermolecular I · · · I contacts linking molecules into either two-dimensional corrugated sheets22 or an infinite three-dimensional lattice.23 In the reactions of iodine with 1,3,5-trithiacyclohexane and 1,3,5-triselenacyclohexane 1: 1 molecular adducts are formed.24 The sulfur-containing complex is a polymeric chain with iodine bridges whilst the selenium-containing complex contains molecular units.24 Whilst chlorine and bromine oxidise dimethylselenide, Me 2 Se and I 2 react to give a 1: 1 charge-transfer complex with a short I–I bond [2.916(3)Å].25 In contrast to the established I · · · I interactions in iodophosphonium ions, evidence for related structures with Br · · ·Br or even Cl · · ·Cl interactions has been extremely scarce.This year, two groups report crystal-structure verifications of these interactions in which monomeric ion pairs [R 3 PX]`· ·· X~ (R\Pr*, X\Cl or Br; R\Pr/, X\Cl) are present.26,27 The work on pre-reactive intermediates of the halogens (and interhalogens, see 126 E.G.HopeFig. 1 Crystal packing for 2,3,5,6-tetrakis(2-pyridyl)pyrazine–iodine adduct (1: 2) (Reproduced by permission from J. Chem. Soc., Perkin Trans. 2, 1997, 2781) below) with a series of Lewis bases continues apace.28–31 Of particular interest this year are the e§ectively planar H 2 O· · ·F 2 adduct [d(O · · · F) 2.719(4)Å]29 and the Mulliken inner complex [Me 3 NF]`F~ formed in the reaction between fluorine and trimethylamine.30 Work in this area has been highlighted.31 3 Interhalogen compounds and polyhalide anions Although VSEPR theory can be used to rationalise, qualitatively, the geometries of halogen fluorides, quantitative predictions have proved more di¶cult.Density functional theory calculations have been used to predict molecular structures and thermodynamic data for ClFn and ClFn ~ (n\1–7) in reasonable agreement with experimental data.32 Vapour pressure data for ClF 3 (300–317 K) has been tabulated33 and the crystal structure of ClF, determined at [188 °C, represents the only example of a halogen monofluoride structure.34 The structure is not like a- or b-ICl or IBr.The ClF molecules form infinite planar ribbons characterised by very short intermolecular Cl · · ·Cl contacts [3.070(1)Å]. The chlorine atoms are arranged in a zig-zag fashion to maximise Cl · · ·Cl contacts and the Cl–F bond length is identical to that derived from 127 Halogens and noble gasesgas-phase electron-di§raction studies.Chlorine monofluoride is used to oxidise SOF 2 , in the presence of activated CsF, to SF 5 OCl,35 (2,6-F 2 C 6 H 3 )IF 4 has been prepared by the nucleophilic fluorine–aryl substitution reaction of IF 5 with (2,6-F 2 C 6 H 3 ) 3 Bi36 and fluorination of C 60 dissolved in CCl 4 with IF 5 gives C 60 Cl 18 F 14 .13 The chargetransfer complexes [Cl–I–C–– – C–Ph]~ (as the [Ph 3 MeP]` salt )37 and R 2 SeIBr (R\Ph or Me)38 have been structurally characterised.The compound Me 2 SeIBr, which lies on the ionic/covalent borderline, is prepared, along with [Me 3 Se]`[IBr 2 ]~, from the reaction of Me 2 Se with IBr. The gas-phase pre-reactive intermediates between ClF and cyclopropane, buta-1,3-diene, methylenecyclopropane, allene and 2,5- dihydrofuran have been identified39 and the data from all sixteen of the Lewis base · · · ClF complexes studied in the last 3 years has been drawn together and compared with the related HCl adducts.40 Density functional calculations on the ethyne–ClF charge-transfer complex predict accurately the rotational constants and intermolecular bond distances allowing the intermolecular energy (3.4 kcal mol~1) to be calculated with some confidence.41 The nature of chemical bonding in hypervalent molecules has always fascinated chemists.In a comprehensive paper, bonding in the X 3 ~ and X 2 Y~ anions has been analysed using a range of theoretical treatments from qualitative molecular orbital theory to density functional calculations.42 It is concluded that the bonding in all the anions can be understood in terms of the Rundle–Pimentel scheme for electron-rich three-centre bonding.Following the widespread use of solid organic tribromides as a practical source of electrophilic bromine, [Et 4 N]`Cl 3 ~ has been found to be a versatile reagent for chlorinations and oxidations in organic chemistry.43 Polyiodide anions have been extensively investigated (see below), but polybromide anions have received less attention due, in part, to their lower stability and the lower tendency of bromine to catenate.The structural characterisation of tribromide anions as tris(diethylamino)benzylphosphonium,44 benzyltriphenylphosphonium,45 tetramethylphosphonium46 and quinuclidinium46 salts illustrate structural variations from linear symmetrical to very distorted anions and a novel, centrosymmetric planar, roughly Z-shaped, anion has been observed in diquinuclidinium octabromide.46 XRay structural characterisation of [1,3,5-trialkyl-2,2,4,6-tetrahydro-1,3,5-triazinium] `In ~ salts (alkyl\Et, n\3; Pr*, 3 or 5; Bu5, 3, 5 or 7) reveal linear symmetric triiodide anions, either isolated V-shaped pentaiodide anions or double layers (cationic and anionic) in which triiodide parts of di§erent anionic layers are linked by iodine molecules to give zig-zag chains, and a three-dimensional network of alternating trigonal pyramidal and Z-shaped heptaiodide anions.47 In [Cu(Dafone) 3 ]I 12 , iodine –iodine interactions assemble novel, planar, I 12 2~ anions into a network around the strained tris-chelate complex of CuII 48 whilst in [(C 5 H 5 ) 2 Fe] 3 I 29 , the most iodinerich polyiodide, the ferrocenium cations are intercalated in the cavities of an anionic three-dimensional network cage structure described by the formula [MI 5 ~) " ·I 2N·M(I 12 2~) " ·I 2N·I 2 ].49 Single-crystal structure determinations of IF 2 ~, ClF 4 ~ and IF 4 ~, as their 1,1,3,3,5,5-hexamethylpiperidinium salts, reveal the expected anion geometries with very little distortions.50 In contrast, the anion in NO`ClF 4 ~ is distorted as a result of N· · ·F interactions.50 In a series of related papers, Minkwitz et al.describe the reactions of CF 3 OCl with polyhalide anions as their Me 4 N` salts. Oxidation of ICl 2 ~ or ICl 4 ~ at [70 °C gives IF 6 ~,51 whilst reaction with Br 3 ~ gives 128 E.G.HopeFig. 2 Chains of (IO 2 )2` and S 2 O 7 2~ in (IO 2 ) 2 S 2 O 7 (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 255) CF 3 OBr·Me 4 N`BrF 2 ~ as an intermediate which decomposes to CF 3 OBr on sublimation. 52 Reaction with BrCl 2 ~ at [70 °C gives Me 4 N`[Br(OCF 3 ) 2 ]~53 which on warming decomposes to Me 4 N`BrF 2 ~. This anion, which had been identified previously, is isoelectronic with KrF 2 and spectroscopic studies confirm that it is linear.54 Further studies and a review of covalent azides including halogen azides have been published.55 4 Halogen oxides and organoiodine oxygen compounds Two timely reviews on halogen oxides56 and bromine oxides57 have appeared which detail the historical relevance of this area (the first halogen oxide was identified by Davy in 1815), the notorious instability of halogen–oxygen bonds and the advent of new preparative and analytical techniques which have initiated a revival in this field.For the bromine oxides, the realisation that the only well-characterised compounds use all the possible combinations of the only basic units in this area (i.e. terminal OBr and pyramidal O–BrO 2 in Br–O–Br, Br–O–BrO 2 and O 2 Br–O–BrO 2 ) suggests that any new homoleptic bromine oxides are likely to be even less stable than these derivatives.57 Reports on the structural characterisation of four bromine oxide compounds have appeared.58,59 The hydrolysis of BrOTeF 5 o§ers a new route to Br 2 O, a compound which has been known for nearly 60 years.Structural analysis indicates that the compound is bent [114.2(2)°] with strong Br · · ·Br interactions in the solid state resulting in chains.58 Intermolecular Br · · ·O contacts also lead to chain formation in the solid state for BrONO 2 , prepared by the halogen exchange reaction of bromine with ClONO 2 .59 Rhombohedral BrO 2 F has six-fold disorder making the oxygen and fluorine atoms indistinguishable by X-ray crystallography, whilst the related compoundO 2 BrOTeF 5 , prepared by ozonolysis of BrOTeF 5 , has the expected pyramidal geometry at the BrO 3 group.58 The significant di§erences in the highresolution IR spectra of mono-isotopical samples of perchloryl fluoride (F35@37Cl16@ 18O 3 ) have been accounted for by the fact that the 18Oisotopomers are much closer to spherical top molecules.60 Careful control of the reaction parameters in the I 2 O 5 –SO 3 –H 2 Osystem allows precipitation of crystalline (IO 2 ) 2 S 2 O 7 .X-Ray analysis reveals that this iodyl compound contains dimeric cations (IO 2 ) 2 2` connected by disulfate groups to give polymeric strands (Fig. 2).61 Flash pyrolysis of I 2 –O 2 –Ar gas mixtures gives the iodine peroxy radical IOO· which, upon irradiation in a lowtemperature matrix, rearranges to iodine dioxide.62 A crystallographic study has revealed that the anions in metaperiodic acid are one-dimensional chains of cis-edge 129 Halogens and noble gasesFig. 3 An ORTEP drawing of a single disordered IO 4 ~ anion showing a detailed view of the rotational disorder about one I–O axis. (Reproduced by permission from Inorg.Chem., 1997, 36, 2564) shared distorted IO 6 octahedra.63 In this work it is noted that, with the exception of H 5 IO 6 and HIO 4 , the proposed constitutions of the other iodine(VII) acids are based on insu¶cient experimental data; i.e. H 7 I 3 O 14 in the solid state is a stoichiometric H 5 IO 6 ·2HIO 4 phase.63 Spectroscopic and structural studies on Me 4 N`IO 4 ~ (prepared by neutralization of aqueous ammonia with periodic acid) confirm Pauling’s 1930 proposal that the phase change in this system is due to the onset of free ion rotation and is not caused by positional disorder of the rotational oscillation axes.64 In the room-temperature structure (Phase II), distorted IO 4 ~ anions undergo free rotation about one of the I–Obonds (Fig. 3) whilst in the Phase III structure (determined at [30 °C) the IO 4 ~ anions are ordered.In the area of kinetic and spectroscopic studies on halogen oxides which are believed to play a role in ozone depletion, investigations on ClO,65 BrO,66 ClO 2 ,67 ClONO 2 68 and BrONO69 have been described. A book on hypervalent iodine reagents in organic synthesis represents a good introduction to this important and rapidly expanding area of chemistry with a strong emphasis on applications.70 Bis-acetoxy-, trifluoroacetoxy- and -p-methylbenzoxyiodobenzenes (I) are valuable reagents as oxidants,71 in the synthesis of diaryliodonium salts,72 in photochemical cyclization reactions73 and in a new and potentially practical approach to the detection of pentachlorophenol, one of the most 130 E.G.HopeO C I Ph O C O R R O R = CH3, CF3 or C6H4CH3- p I toxic polychlorinated phenols.74 A series of compounds, RI(ONO 2 ) 2 , have been prepared by the reaction of RI (R\Me, Me 3 Si or CN) with ClONO 2 .75 5 Cationic iodine and other organoiodine compounds An easy route to symmetrical and unsymmetrical diaryliodonium salts via oxidative anion metathesis of diaryliodonium diodides and chlorides has been described.76 The observation that PhI(OH)(OTs) and PhI(OH)(OSO 2 Me) ionize completely in water to [PhIOH]`, with evidence for the k-oxo dimer [Ph(OH)I–O–I`(OH 2 )Ph] at signifi- cant concentrations, has important implications for the use of these reagents for organic synthesis in water or un-dried organic solvents.77 Derivatives of polyvalent iodine with an alkyl substituent at iodine are generally highly unstable.However, monocarbonyliodonium ylides (II), which are stable up to[30 °C, are formed according to equation (1),78 chiral alkynylphenyliodonium tosylates (III) have been reported, 79 and (p-tolyl)sulfonylmethyliodonium triflate represents the first structurally [R I(Ph)]BF4 AcO R I(Ph)Br R R1 O O– I+Ph (i) AcOH (ii) NaBr (aq) EtOLi R1CHO II (1) R* C C IPh OTs R = C2H5C*H(CH3)CH2O or C2H5C*H(CH3)CH2OCO III characterised compound with an I–C41 bond.80 Four new iodonium ylides (RINSO 2 R@)81 have been prepared and structurally characterised as either a layered structure (R\m-tolyl, R@\p-nitrophenyl), two-dimensional ladders (R\m-tolyl, R@\phenyl or p-tolyl) or a three-dimensional stepladder (R\R@\p-tolyl), illustrating that minor perturbations of the aromatic rings have substantial consequences on the supramolecular assemblies of these materials.Although diaryl- and dialkyl-iodonium ions are well established, relatively little is known about divalent iodine (9-I-2, i.e. a series of iodine atoms with nine valence electrons and two donor ligands) radicals.Evidence for these radicals has been obtained by the homolytic cleavage of I–O bonds during thermolysis of (tert-butylperoxy) iodanes (IV).82 131 Halogens and noble gasesFig. 4 An ORTEP drawing of p-tert-butylcalix[4]arene·C 6 H 5 NO 2 ·Xe adduct showing only the Xe guest (Reproduced by permission from Chem. Commun., 1997, 939) O I R2 O2But R1 R1 R1 = CH3, R2 = H or OCH3 R1 = CF3, R2 = CH3 IV 6 Noble gases In the gas phase, helium and neon do not react with F 2 ·` (see above) whilst krypton and xenon react at the collision-controlled limit to give Ng·`]F 2 .Interestingly, argon o§ers two reaction pathways giving Ar·`]F 2 and Ar–F`]F· in comparable amounts.12 Liquid argon (93–125 K) has been used as the solvent for the spectroscopic characterisation of 1: 1 van der Waals complexes between ethene or propene and BF 3 ,83 and CH 3 F and BFxCl 3~x (x\1 or 2).84 Fast time-resolved IR spectroscopic studies have identified CpRe(CO)(A) (A\Kr or Xe) in supercritical noble gas solutions85 and supercritical xenon has been used as a solvent to investigate the solution photochemistry of trans-Cp*Re(CO)(H 2 ).86 Recent studies utilising 129Xe NMR for structural investigations of solids include mixed Br 2 –Xe hydrates,18 microporous polymers,87 xeolites88 and, for the first time, in the p-tert-butylcalix[4]arene·C 6 H 5 NO 2 ·Xe adduct (Fig. 4), 129Xe NMR spectral features have been related to specific structural aspects.89 Enhancement in sensitivity and resolution is a recurring theme in the field of NMR spectroscopy and this year heralds significant advances in polarisation transfer from laser-polarised 129Xe to 1H spins in 132 E.G.HopeFig. 5 Stereoview of the unit cell of [Xe(2,6-F 2 C 6 H 3 )][OSO 2 CF 3 ] (Reproduced by permission from Z. Anorg. Allg. Chem., 1997, 623, 1821) solution,90 on surfaces91 and in a continuous-flow system.92 Hyperpolarised xenon has been used in the liquid phase for the first time,93 which may open the way for polarisation transfer in supercritical xenon. 7 Noble gas compounds Fully relativistic all-electron Dirac–Fock and Dirac–Fock–Breit calculations for XeFn (n\1, 2, 4 or 6) have been undertaken. Surprisingly, relativistic e§ects are almost negligible and the calculations give Xe–F distances in good agreement with experimental data.94 Nineteen years after Stein et al.reported the existence of the dark green Xe 2 ` cation, a structural characterisation, as the Sb 4 F 21 ~ salt, has confirmed the presence of a Xe–Xe bond [3.087(1)Å].95 This interaction is longer than any other main-group element–element bond, and must be considered to be weak. The cation is only observed in ‘magic acid’ (HF–SbF 5 ) and the potential role of H` in the oxidation of xenon is discussed.Xenon bis(trifluoroacetate) reacts with triflic acid to give the highly reactive CF 3 CO 2 XeOSO 2 CF 3 .96 Upon reaction with aryl substrates, a range of cationic xenon trifluoromethanesulfonates can be identified, including the structurally 133 Halogens and noble gasescharacterised [Xe(2,6-F 2 C 6 H 3 )][OSO 2 CF 3 ] (Fig. 5), for which the non-bonded Xe · · · F distance [3.098(6)Å] is 12% shorter than the sum of the van der Waals radii. This is used to support the claim that fluorine atoms in the 2- and 6-positions increase the thermal stability of xenon–aryl cations. The first evidence for covalent Kr–O bonding in the gas phase arises from Fourier-transform ion cyclotron resonance mass spectrometric investigations of the reactions of krypton with cationic ozone derivatives where stable KrOn ` (n\1 or 2) and KrOH` ions have been identified.97 Xenon compounds continue to find applications in inorganic and organic chemistry.The influence of emission activators on chemiluminescence from the reaction of (EtO) 2 AlEt with XeF 2 has been studied.98 Xenon difluoride is an oxidant in the synthesis of (2,6-F 2 C 6 H 3 ) 3 BiF 2 ,36 IF 2 ~ and IF 4 ~salts,50 E(C 2 F 5 ) 3 F 2 (E\As or Sb),99 [PtF 2 (py) 4 ][BF 4 ] 2 100 and [RuF 2 (CO) 3 ] 4 .101 Although PhSeCl and PhSeBr are commercially available sources of selenic electrophiles, PhSeF is too labile to be isolated.It can be generated in situ from PhSeSePh and XeF 2 102 and has been used to generate novel phosphaalkenes from phosphaacetylenes. Speculation that FXe(N 3 ) and FXe(NCO) may have been formed, transiently, in the reactions of XeF 2 with azide or cyanate ions is based solely on the distribution of decomposition products.103 The reaction of XeF`AsF 6 ~ with HI does not give xenon–iodine compounds and Xe, HF and [I 4 ][AsF 6 ] 2 were identified as the final reaction products.104 Ab initio calculations confirm that it is unlikely that the [XeI]` cation could be identified in solution (i.e.without crystal-lattice stabilization). References 1 A. J. Cormack, A. J. Yencha, R. J. Donovan, K. P. Lawley, A. Hopkirk and G. C. King, Chem. Phys., 1996, 213, 439. 2 D.E. Williams and D. Gao, Inorg. Chem., 1997, 36, 782. 3 M.D. Levin, S. J. Hamrock, P.Kaszynski, A. B. Shtarev, G. A. Levina, B. C. Noll, M. E. Ashley, R. Newmark, G. G. I. Moore and J. Michl, J. Am. Chem. Soc., 1997, 119, 12 750. 4 R.E. Banks, M. K. Besheesh, S. N. Mohialdin-Kha§af and I. Sharif, J. Fluorine Chem., 1997, 81, 157. 5 R.D. Chambers, J. Hutchinson, G. 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ISSN:0260-1818    

DOI:10.1039/ic094124

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

10 Zinc, cadmiumand mercury By I. B. GORRELL School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton, BN1 9QJ, UK 1 Introduction This report covers the literature for 1997 and is in the same format as last year with the emphasis on organometallic and co-ordination chemistry. In general, compounds containing open-chain polydentate and macrocyclic ligands are not included. 2 Zinc Carbon-donor ligands The preparations and structures of [ZnBz 2 (tmen)], [ZnMCH(SiMe 3 )PhN2 (tmen)] and [ZnMCH(SiMe 3 )PhNMN(H)Si(SiMe 3 ) 3N(tmen)] have been reported.1 Reaction of [MgBz 2 (thf) 2 ] with ZnBz 2 in thf yielded [Mg(thf) 6 ][ZnBz 3 ] 2 which was shown by X-ray di§raction to contain trigonal planar zinc. The compound is cleaved by tmen to givea mixture of [MgBz 2 (tmen)] and[ZnBz 2 (tmen)].2 Alsopossessing trigonal-planar zinc were [Na(12-crown-4) 2 ][ZnMN(SiMe 3 ) 2N3 ] and the [Zn(C–– – CPh) 3 ]~ salt, prepared fromthe amide by reaction with PhC–– – CH.3 The structures of [Li 2 ZnMe 3 (CN)] and [Li 2 ZnMe 3 (SCN)] have been shown by EXAFS to be tetrahedral zincates.4 Lithium zincates with intramolecular Li–N bonding, [Li(thf)nZn(C 6 H 4 CH 2 NMe 2 - 2) 3 ] (n\0 or 1) and [Li 2 Zn(C 6 H 4 CH 2 NMe 2 -2) 4 ] have been prepared and structurally characterized by X-ray di§raction. Reaction of [LiCH 2 SiMe 3 ] with [Zn(C 6 H 4 CH 2 NMe 2 -2) 2 ] gave the homoleptic zincate complexes rather than a mixed species.5 The syntheses and reactivity of penta- and deca-zincated ruthenocenes have been reported.6 The preparations, structures and reactivities of [M(SiBu5 3 ) 2 ] (M\Zn, Cd or Hg) and [M(X)SiBu5 3 ] (M\Zn or Hg,X\Cl;M\Cd, X\I) have appeared; [Zn(Br)SiBu5 3 ] and [ZnCl(L)SiBu5 3 ] (L\thf or tmen) were also prepared.The disilyl species were monomeric and [Zn(Br)SiBu5 3 ] and [Hg(Cl)SiBu5 3 ] were tetrameric.7 Nitrogen- and phosphorus-donor ligands Reaction with dialkyl carbonates or with an alcohol and CO 2 converted [LZn(OH)] (L\TpC6.,M% or TpB65,M%) into the alkyl carbonates [LZn(OCO 2 R)].The [LZn(OH)] f[LZn(OCO 2 Me)] (L\TpC6.,M%) interconversion was carried out by bubbling 137either CO 2 or N 2 through the [LZn(OH)] or [LZn(OCO 2 Me)] solutions; [LZn(OH)] catalysed the formation of diethyl carbonate fromCO 2 and EtOH. Loss of CO 2 from [TpB65,M%Zn(OCO 2 R)] (R\Me or Et) under high vacuum yielded alkoxides. 8 Reaction of [LZn(OH)] (L\TpB65,M%, TpP),M% or TpC6.,M%) with acidic alcohols or phenols gave the corresponding alkoxides or phenoxides.9 The preparation of [TpR,M%ZnF] (R\p-tolyl or Bu5) and its reactions with py–BF 3 to give [LZn(py)]- [BF 4 ] (L\Tpp-50-,M%), with Me 3 SiX (X\H, Cl, Br, I, NCO or OAc) to give [LZnX] and with bis(trimethyl)malonate to yield [LZnOC(O)CH 2 C(O)OZnL] have been described.10 A series of compounds [Zn(NR 2 ) 2 ] (R\Et, Pr* or Bu*) and [RZnNR@2 ] (R\Me or Et; R@\Et, Pr*, Bu* or SiMe 3 and R\CH 2 Bu5 or Bu5; R@\Et, Pr* or Bu*) have been prepared as potential precursors for MOCVD but only [RZnNR@2 ] were su¶ciently volatile.11 A series of alkyl(dialkylamido)zinc compounds [ZnRMeM(CH 2 )nNMe 2N] 2 (n\2 or 3; R\Me or Et) have been isolated.When reactions were carried out with traces of moisture present, [Zn 6 R 4 O 2MMeN(CH 2 )nNMe 2N4 ] were obtained. X-Ray analysis showed the latter to contain a central Zn 2 N 2 ring edged by four Zn 2 NOrings; the dimers also contained Zn 2 N 2 rings and all metal centres had tetrahedral geometry. 12 The compounds [Zn(NBu* 2 ) 2 ] and [Zn(NBu5 2 ) 2 ] were dimeric and monomeric, respectively, in the gaseous, liquid and solid states.13 The preparations of [ZnCl 2MMe 3 SiNP(CH 2 ) 4 CMe 3N] 2 , [ZnI 2MMe 3 Si(NPEt 3 )N] 2 , [ZnI 2MMe 2 Si(NPEt 3 ) 2N], [ZnX(NPEt 3 )] 4 (X\Br or I) and [ZnBr(NPMe 3 )] 4 have been reported; several were crystallographically characterized.14 The neutral radical complex [Zn(Bu5NCHCHNBu5)(CH 2 ) 3 OMe] and the radical anions [ZnR 2 (Bu5- NCHCHNBu5)]~ (R\Me or Et) have been prepared as part of a study of the proposed intermediacy of organozinc radicals in the regioselective alkylation reactions of Bu5NCHCHNBu5 with ZnR 2 .The anions are unstable and undergo an intermolecular single-electron transfer to give [ZnR(Bu5NCHCHNBu5)]~ and [ZnRMBu5- NC(R)CHNBu5N]~.15 Zinc and cadmium complexes derived from N-[(2-pyrrolyl) methylidyne]-N@-tosylbenzene-1,2-diamine, H 2 L, have been prepared electrochemically; [Zn(HL) 2 ] possessed a distorted tetrahedral structure.16 Reaction of ZnCl 2 with 2-pyridylmethanol (HL) in diethyl ether yielded [(HL) 2 Zn(k- Cl) 2 Zn(HL) 2 ][ZnCl 4 ] whereas reaction of Zn[N(SiMe 3 ) 2 ] 2 with HL in dichloromethane yielded [Zn(ZnL 2 ) 6 ]Cl 2 in which the central ZnO 6 octahedron was surrounded by six ZnO 4 N 2 units; the cations represent fragments of the CdI 2 structure.17 An orange-light-emitting complex [ZnL 2 ] (L\2-styryl-8-quinolinolato) has been synthesised and used in electroluminescent devices.18 Networks based on [Zn(4,4@-bipy)(H 2 O) 4 ]2`·n4,4@-bipy (n\1, 1.5 or 2) in which cross-linking occurs through hydrogen bonding between water molecules and the free bipy molecules, have been prepared.19 The crystal structures of [Zn(bipy)(O 2 CCCl 3 ) 2 (H 2 O)], [Zn(phen)(O 2 CCCl 3 ) 2 (H 2 O)] and [Zn(k-4,4@-bipy)(4,4@- bipy) 2 (O 2 CCCl 3 ) 2 (H 2 O) 4 ]n showed trigonal bipyramidal co-ordination at zinc for the bipy and phen complexes and octahedral geometry for the polymer with Zn(H 2 O) 4 units bridged by the 4,4@-bipy ligands.20 The crystal structure of M[Zn 2 (4,4@- bipy) 3 (NO 3 ) 4 ]·2H 2 ONn revealed distorted pentagonal-bipyramidal metal centres bridged by 4,4@-bipy ligands to give a three-dimensional framework.21 The crystal structures of [Zn(dmphen) 2 (NO 3 )][NO 3 ] and [Zn(dmphen) 2 ][BF 4 ] 2 , containing five- and four-co-ordinate zinc, respectively, have been reported.22 Reactions of ZnO 138 I.B.Gorrellwith [NH 4 ][NCS] and dabco in an organic solvent have led to the isolation and crystallographic characterization of [Zn 2 (NCS) 4 (NH 3 ) 2 (dabco)] and [Hdabco] 2 [Zn(NCS) 4 ] both with four-co-ordinate zinc and polymeric [Zn(NCS) 2 (dabco)(dmso)] with five-co-ordinate zinc.23 Another five-co-ordinate zinc complex [Zn(Hdabco)(H 2 O)(NO 3 ) 3 ] was obtained using an analogous procedure with [NH 4 ][NO 3 ].24 The structure of [ZnL 2 (NO 3 ) 2 ]·4.5H 2 O [L\1,4-bis(imidazol- 1-ylmethyl)benzene] revealed a new type of two-dimensional polyrotaxane with zinc in a distorted tetrahedral environment.25 The formation energies and most stable structures for [M(NCS) 4 ]2~, [M(NCS) 2 (SCN) 2 ]2~, [M(SCN) 4 ]2~ (M\Zn, Cd or Hg) and [Cd(NCS) 3 (SCN)]2~ have been calculated.26 The crystal structure of [ZnClMCH(Me)PEt 2NMNSiMe 3N] 12 showed six eight-membered rings with metal centres within and between the rings linked through Zn–Cl–Zn bridges.27 The preparations and crystal structures of [MI 2MP(SiMe 3 ) 3N] 2 (M\Zn or Cd), [NBu/ 4 ] 2 [Zn 6 I 6 (PSiMe 3 ) 4 (thf) 2 ]·C 6 H 6 , [NBu/ 4 ] 2 [Cd 4 I 8MP(SiMe 3 ) 2N2 ], [Zn 4 Cl 4ME(SiMe 3 ) 2N4 (MeCN) 2 ] (E\P or As) and [Zn 10 Cl 12 (PSiMe 3 ) 4 (PEt 2 Ph) 4 ] have appeared.All structures are based on adamantane cores (four in the Zn 10 species) except the dimers and compound 1.28 Oxygen- and sulfur-donor ligands The syntheses and crystal structures of [Zn 0.78 Fe 0.22 O(OAc) 6 (py) 3 ]·py, [Fe 2 ZnO(OAc) 6 ]·py, [Zn 2 Fe(OAc) 6 (py) 2 ]·py, [Zn(OAc) 2 (py) 2 ], [Zn(OAc) 2 (py)] 2 , [Zn(OAc) 2 (py)]n, and [Zn 3 (OAc) 6 (py) 2 ] have been reported as part of a study of the syntheses, reactivity and catalytic behaviour of iron–zinc systems involved in the oxidation of hydrocarbons under Gif-type conditions.29 The structure of the octahedral complex [Zn(O 2 CCH 3 ) 2 (H 2 O) 2 ] has been redetermined.30 The crystal structure of [Cu 0.06 Zn 0.94 C 4 O 4 H 2 ]·2H 2 O showed a two-dimensional polymer with layers containing five-co-ordinate metal atoms interconnected by tridentate maleate anions.Thermal decomposition gave ZnO and CuO.31 The crystal structures of [ZnL 2 (H 2 O)Cl][ClO 4 ] and [ZnL 3 (H 2 O)][ClO 4 ] 2 (L\Me 3 N`CH 2 CO 2 ~) revealed tetrahedral metal centres.32 The synthesis, structure and selective guest binding of a three-dimensional zinc(II) benzenetricarboxylate network have been reported.33 Addition copolymerisation of cis, cis-1,3,5-cyclohexanetricarboxylate (ctc) with zinc(II) and py in dmf solution yielded the extended co-ordination solid [Zn 3M(ctc)(py)N2 ·2dmf]; the structure contains 6Å diameter channels.34 The syntheses and structures of 139 Zinc, cadmium and mercury[NHEt 3 ][ZnCl 2 L] MHL\2-[(diethylamino)methyl]phenol or 2-[(diethylamino) methyl]-4-methylphenolN have appeared.The tetrahedral metal centres (N,O) were part of six-membered rings.35 The three metal centres in the ten-membered ring compound [Zn 2 (dmphen) 2 (k-OH)(k-S 2 O 3 ) 2 Na(H 2 O) 3 ]·2H 2 O·MeOH were bridged by oneOHand two S 2 O 3 groups.36 The hydration and water exchange mechanisms of [Zn]2` have been studied using density functional calculations.37 A monomeric 1: 3 adduct between Zn(iso-mnt) and 3-methylpyridine has been crystallographically characterized.38 The crystal structure of [Zn 2 (iso-mnt) 2 (4-Mepy)] showed dimeric units based on a Zn 2 S 4 C 2 ring with tetrahedral metal centres; the base-free analogue was also dimeric.39 The crystal structure of [Zn(S 2 CNPr*Me) 2 (tmen)] revealed tmen in an unusual (for a Group 12 metal) bridging mode; [Zn(S 2 CNPr*Me) 2 (py)] was monomeric.Both complexes contained zinc in a square-based pyramid.40 The synthesis and structure of the enantiomerically pure S,N-chelated complex [(R,R)-ZnMSC 6 H 4 C(Me)HNMe 2 -2N2 ] has been reported, together with its role as a catalyst for the addition of dialkyl zinc compounds to aldehydes.41 The use of [NMe 4 ] 2 [Zn(SPh) 4 ] as a model for the [Zn(Cys-S) 4 ]2~ site in the Ada protein of Escherichia coli has been described.Mechanistic studies of methyl transfer from (MeO) 3 PO involving a series of model complexes were consistent with a dissociated thiolate as the active species.42 The electronic structures of a series of benzenethiolate-capped clusters [Zn(SPh) 4 ]2~, [Zn 4 (k-SPh) 6 (SPh) 4 ]2~, [Z� 10 (k3 - S) 4 (k-SPh) 12 ] and [Zn 10 (k3 -S) 4 (k-SPh) 12 (SPh) 4 ]4~ have been investigated by coupling density functional calculations to UV- and X-ray photoelectron spectroscopy.The neutral species was found to be a reasonable mimic of solid ZnS.43 A series of metal thiocarboxylates [M(SOCR) 2 L 2 ] (M\Zn or Cd; R\Me or Bu5; L\3,5-dimethylpyridine) have been fully characterized as tetrahedral complexes with monodentate S-bound anionic ligands.Heating the cadmium derivatives in solution yielded CdS (sphalerite).44 The dimethylthioformamide solvates of the divalent Group 12 ions are tetrahedral for zinc, octahedral for cadmium and linear for mercury (made octahedral by Hg· · ·O secondary bonding from ClO 4 ~).45 Using large-angle X-ray scattering zinc(II) and mercury(II) ions in dimethylthioformamide were found to co-ordinate four solvent molecules in solution, whereas cadmium was six-co-ordinate.Vibrational spectra were also recorded and explanations for the change in co-ordination number were discussed in terms of the second-order Jahn–Teller e§ect.46 The crystal structures of [NEt 4 ] [ZnL 2 ], [FcCH 2 NMe 3 ] 2 [ZnL@2 ] and [FcCH 2 NMe 3 ] 2 [ZnL 2 ] (L\1,3-dithiole-2- one-4,5-dithiolate, L@\1,3-dithiole-2-thione-4,5-dithiolate) were discussed with reference to the e§ects of the cation on crystal packing.47 Reactions between zinc thiourea and thiosemicarbazide complexes and the terephthalate anion showed that ligand lability was important in determining whether a hydrogen-bonded polymer or a co-ordination polymer was obtained.48 The preparations and crystal structures of [S 2 MS 2 M@I 2 ]2~ (M\Mo or W; M@\Zn, Cd or Hg), containing two edge-sharing tetrahedra, have been reported.49 Halogen-donor ligands Several crystal structures of tetrachlorozincates50 as well as [Cu(C 10 H 24 N 4 )(k-Cl) ZnCl 3 ],51 [ZnCl 3 (thf)]~ and [ZnCl 2 (thf) 2 ]52 have appeared. 140 I.B. Gorrell3 Cadmium Nitrogen- and phosphorus-donor ligands The structure of trans-[CdL 2MAg(CN) 2N2 ]n [L\1,3-di(4-pyridyl)piperidine] consisted of a doubly interpenetrating three-dimensional framework.53 In the structure of [CdL 2MAg(CN) 2N]n·n[Ag(CN) 2 ] [L\N-(2-aminoethyl)piperazine], L and CN~ ligands bridge octahedral cadmium and tetrahedral silver centres to form a threedimensional cationic host network accommodating [Ag(CN) 2 ]~ as guest.54 The anionic three-dimensional network [Cd 8 (CN) 19 ]3~ has been shown by X-ray crystallography to form a clathrate complex with [Cd(dien) 2 ]2` and [Cd 2 (CN) 3 (dien) 2 ]` as guests.55 The crystal structures of the morpholine complex [Cd(C 4 H 9 NO) 2 Ni(CN) 4 ] and the dioxane-guest clathrates [Cd(H 2 O) 2 M(CN) 4 ]·2C 4 H 8 O 2 (M\Ni or Cd) have been reported.Similarities with known structures were discussed.56 A chiral co-ordination polymer, CdM[C(CN) 3 ][B(OMe) 4 ]N·xMeOH (x[1.6), containing seven-co-ordinate cadmium has been reported.57 The crystal structures of [CdX(pyca)] (X\N 3 or NCS) revealed octahedrally co-ordinated metal centres; the azide containing sheets of polyhedra and the thiocyanate one-dimensional chains.58 The crystal structures of [CdX 2 (pyz)] (X\Cl, Br or I) showed infinite CdX 2 chains with pyz ligands completing the octahedral co-ordination at the metal and linking the chains to form layers.59 The crystal structures of [CdX 2 L] (L\pyz; X\Br or I) and [CdL(NO 3 ) 2 ]·2H 2 O (L\pyrimidine) have appeared.The pyrazine compounds consisted of two-dimensional networks of M–L–M and M–X 2 –M chains whereas the pyrimidine complex has a three-dimensional structure due toM–L–Mchains connected by hydrogen bonds.60 The synthesis and structure of [CdI 2 (k-dppy) 2 Ir(CO) 2 I] with a donor–acceptor IrI–CdII bond has been reported.A long-lived metal–ligand charge-transfer excited state was observed.61 The absorption of CO 2 from air by [CdL 3 ][ClO 4 ] 2 to give the crystallographically characterized [Cd 2 L 4 (k-CO 3 )(H 2 O)] [ClO 4 ] 2 ·H 2 O (L\N@-isopropyl-2-methylpropane-1,2-diamine) has been observed.62 Crystallisation of [Cd(phen) 3 ][ClO 4 ] in the presence of 4-nitroaniline (L) yielded a 1: 2 adduct which exhibited weak second harmonic generation activity (possibly due to disorder) even though it possessed a centrosymmetric space group.63 Addition of Cd[N(SiMe 3 ) 2 ] 2 to a LiBu/–[(mes) 2 P(H)––O] mixture gave the diorganophosphinite [M(Me 3 Si) 2 NNCdM(mes) 2 P–ON2 Li·2thf] with a trigonal-planar cadmium centre.64 Oxygen-donor ligands Square-planar co-ordination geometries were observed in [Cd(OC 6 H 3 Bu5 2 - 2,6) 2 (thf) 2 ] and [Cd(OC 6 H 3 Bu5 2 -2,6) 2 (tht) 2 ]; however, [Cd(OC 6 H 3 Ph 2 -2,6) 2 (thf) 2 ] was tetrahedral and [Cd(OC 6 H 3 Bu5 2 -2,6) 2 (py) 3 ] was trigonal bipyramidal with axial py ligands.65 A series of mono-, di-, tri- and tetra-nuclear cadmium complexes of the betaine, Ph 3 P`(CH 2 ) 2 CO 2 ~(L) have been prepared and structurally characterized;66 [CdL 2 (tmen)(H 2 O)][ClO 4 ] 2 ·2H 2 O and [CdI 2 L(tmen)] showed pentagonal bipyramidal and distorted octahedral metal co-ordination, respectively.67 The preparations and crystal structures of [CdCl 2 L 2 (H 2 O)] and [CdX 2 L 2 ] [L\Ph 3 P`(CH 2 ) 3 CO 2 ~; X\Br or I] have appeared68 and the structures of [Cd 3 L 4 (H 2 O) 2 Cl 4 ]n[ClO 4 ] 2n and M[CdL 2 (NO 3 )][ClO 4 ]Nn (L\Me 3 N`CH 2 CO 2 ~) revealed octahedral metal centres.69 The structure of 141 Zinc, cadmium and mercury[Cd(O 2 CCH 3 ) 2MNi(dmf)(saltn)N2 ] shows cadmium in a distorted octahedral environment with apical acetate groups and four bridging oxygen atoms from two saltn ligands in the equatorial plane.70 Reaction of [Cd(OAc) 2 ]·2H 2 O with [Co 3 (CO) 9 (k3 - CC2 H)] in the presence of Me(OCH 2 CH 2 ) 4 OMe (L) a§orded [Cd 2M(CO) 9 Co 3 (k3 - CCO 2 )N4 L] in which the cadmium is seven-co-ordinate in a distorted trigonal-capped square-based polyhedron.71 Sulfur- and selenium-donor ligands The crystal structure of [Cd(tu) 2 Cl 2 ] revealed tetrahedral molecules held together by hydrogen bonding; thermal decomposition did not give clean conversion to CdS.72 The cadmium in [Cd(tu) 6 ][ReO 4 ] 2 ·H 2 O lies at the centre of a trigonal antiprism73 and the structure of [Cd(bipy)(S 2 O 3 )] showed five-co-ordinate cadmium in a Cd 2 S 3 O ring.74 The syntheses, crystal structures and second-order optical non-linearity of tetrahedral [CdL 2 X 2 ] [L\bis(2-chlorobenzaldehyde thiosemicarbazone); X\Br or I] have been reported75 as have the synthesis and structure of [Cd(12-crown-4) 2 ] [Cd 2 (SCN) 6 ] which contained a novel tetragonal net of anionic layers templated by the square-shaped sandwich cations.76 Electrospray mass spectra of the tetramethylammonium salts of [Cd 10 E 4 - (SPh) 16 ]4~ (E\S or Se), [Zn 4 S 4 (SPh) 16 ]4~, [Cd 17 S 4 (SPh) 28 ]2~, [M(SPh) 4 ]2~, [M 4 (SPh) 10 ]2~ (M\Zn or Cd) and [Cd 4 X 4 (SPh) 6 ] (X\Cl, Br or I) have appeared77 and oxidation of the surface-capping thiolate ligands in [Cd 10 S 4 (SPh) 16 ]4~ with iodine has been explored as a route to large, well defined CdS nanocrystals.The results indicated that the iodine substitution is followed by loss of four [Cd(SPh) 4 ] units at the cluster corners to give a Cd 6 S 4 species.78 The syntheses and structures of [Cd 10 Se 4 (SePh) 12 (PPh 3 ) 4 ] and [Cd 16 (SePh) 32 (PPh 3 ) 2 ] have appeared.79 Halogen-donor ligands The structure of [Ph(CH 2 ) 2 NH 3 ] 2 [CdCl 4 ] revealed the metals in a layer structure of corner-shaped octahedra.80 The cis-[Co(en) 2 (OH) 2 ]` cation can act as a ligand to form tetranuclear [Cd 2 (k-Cl)Cl 4M(OH) 2 Co(en) 2N2 ]ClO 4 , in which cadmium lies at the centre of face-sharing octahedra, and polymeric [Cd(k-Cl)(H 2 O) 2M(OH) 2 Co(en) 2N]Cl 2 containing corner-sharing octahedra.81 The preparation, structure and thermal properties of [HL1][CdCl 3 ], [H 2 L2][Cd 2 Cl 8 ]·H 2 Oand [H 2 L3][Cd 2 Cl 6 (H 2 O) 2 ] (L1\1- methylpiperidine, L2\N-methylethane-1,2-diamine, L3\1-amino-4-methylpiperazine) have been reported.All structures contain polymeric chains made up of face-sharing CdCl 6 octahedra, [CdCl 4 ]2~ anions and edge-sharing CdCl 5 (H 2 O) octahedra, respectively.82 The preparation and structure of [Li(MeCN) 4 ][Cd 6 I 16 ] revealed six alternating corner- and edge-sharing CdI 4 tetrahedra.83 4 Mercury Carbon-donor ligands A series of stable organomercury hydrides (deuterides), [HgH(R1O)C(O)C(R2)––C(H)] (R1\Me, CH 2 CMe 2 CH 2 OH or p-NO 2 C 6 H 4 ; R2\H or Et) and their corresponding radicals have been described.Stability was ascribed to the electron-withdrawing e§ect of the acrylic acid moiety.84 The synthesis, structure and reactivity of 142 I.B. Gorrell[(Me 2 N) 3 S] 2 [(CF 3 ) 2 Hg(k-F) 2 Hg(CF 3 ) 2 ], which can act as a source of CF 3 radicals and difluorocarbene, have appeared.85 Hydrolysis of (1,3-dimethyluracil-5-yl)mercury( II) nitrate, [HgL][NO 3 ], yielded two di§erent [Hg 3 L 3 O]` cations, one of which contained a virtually planar Hg 3 Ounit, the other being a flat pyramid.Both dimerised through weak Hg· · ·Hg interactions.86 Reaction of 1,8-naphthalenediylbis[mercury( II) chloride] with InCl in thf yielded the bis(thf) adduct of bis(k-1,8-naphthalenediyl) mercury(II)chloroindium(III).87 The synthesis and crystal structure of 1,3- (ClHgCH 2 ) 2 C 6 H 4 revealed secondary Hg· · ·Cl bonding resulting in a three-dimensional network.88 An MNDO study of the complexes of polymercury-containing macrocycles with halide anions has led to a bonding description independent of the number of metal atoms.89 Mercuration of terephthaldehyde yielded [HgClMC 6 H 3 (CHO) 2 -2,5N] and [HgMC 6 H 3 (CHO) 2 -2,5N2 ]; the aldehyde groups were oxidised to acids.90 A mechanism for the mercuration of ferrocene, based on pre-complexation of the mercurating agent to the iron atom followed by rate-determining formation of the C–Hg bond with concomitant loss of H`, has been presented.91 Symmetrization of some mercurated anils of benzoylferrocene has been achieved by refluxing with PPh 3 ; the crystal structure of [HgM(\Cp)Fe(g5-C 5 H 3 CPh––NC 6 H 4 Br-4N2 ] was reported.92 Mercuration of 1@-benzoyl-1-[(arylimino)phenylmethyl]ferrocenes occurred at the 2- position of the ferrocene ring.93 The synthesis, structure and reactivity of some substituted (cyclobutadiene)(cyclopentadienyl)cobalt complexes in which the cyclopentadienyl rings are pentasubstituted with HgX (X\O 2 CCF 3 or SCH 2 CH 2 OH) groups have been described.94 The synthesis of Hg[C–– – CC–– – CC(NMe 2 )––W(CO) 5 ] 2 has appeared.95 Reaction of [MnL(H 2 O)]ClO 4 with [Hg(CN) 4 ]2~ yielded the one-dimensional polymer [MMnL(H 2 O)NMHg(CN) 3N] and the trinuclear complex [MMnL(H 2 O)N2MHg(CN) 4N] [L\N,N@-(1,1,2,2-tetramethylethylene)bis(salicylideneiminato)].Both were characterized by X-ray crystallography.96 Nitrogen- and phosphorus-donor ligands The preparations and structures of [HgRL] (R\Me or Ph; L\azaindolyl-azaindole) have appeared. In both cases a linear arrangement was observed at the metal.97 The preparations of [HgX 2 (C 5 H 4 NCO 2 R)] (X\Cl, Br or I; R\Me, Et, Pr/ or Pr*) together with the crystal structures for X\Cl have appeared.The compounds are polymeric (R\Me or Et) or six-co-ordinate centrosymmetric dimers (R\Pr/) and tetramers (R\Pr*).98 The MCD spectra for [Hg 3 (dppm) 3 (SO 4 ) 2 ] have been interpreted in terms of 6s 6s p]p* and 6s 6p p]n metal-centred transitions.99 The synthesis, structure and bonding of [HgPBu5] 12 have been reported. It is best described (see Fig. 1) as a trimer of [HgPBu5] 4 units made up of eight-membered rings.100 Oxygen- and sulfur-donor ligands X-Ray crystallographic studies of [Hg(bipy)(O 2 CCF 3 )] 2 [Hg(O 2 CCF 3 ) 4 ], [Hg(bipy)(O 2 CCF 3 )][Hg(bipy)(O 2 CCF 3 ) 3 ] and [Hg(bipy) 2 ][O 2 CCF 3 ] 2 showed the trifluoroacetates to be solely monodentate.101 Reaction of [Hg 2 ]2` with dmpm (two equivalents) or reduction of a mixture of [Hg(dmso) 6 ][O 3 SCF 3 ] 2 and dmpm (2: 4) with mercury a§orded [triangulo-Hg 3 (k-dmpm) 4 ][O 3 SCF 3 ] 4 .102 Symmetrization of [Hg(Ph)EH] (E\O or S) using catalytic amounts of Ni(acac) 2 has been reported to proceed via [Ni(acac) 2 (PhHgOHgPh)] 2 ; the crystal structure of the diethyl ether 143 Zinc, cadmium and mercuryFig. 1 Molecular structure of [(HgPBu5) 4 ] 3 . The black and shaded spheres represent phosphorus and mercury, respectively. (Reproduced by permission from Angew. Chem., Int. Ed. Engl., 1997, 36, 233.) adduct was determined.103 The reactions of [Hg(Ph)OAc] with a series of alkyl, aryl and heterocyclic semicarbazones (L) to form [HgPhL] have been described.104 The demethylation of (MeO) 3 PO using [NMe 4 ][Hg(SPh) 4 ], to give [Hg(SPh) 3 ]~, [(MeO) 2 PO 2 ]~ and MeSPh, and [NBu 4 ][Hg(SPh) 3 ], to give MeSPh and [Hg(SPh) 2M(MeO) 2 PO 2N]~, has been investigated. Kinetic studies indicated free thiolate to be the active species and implications for the mercury derivative of the E.coli Ada DNA alkylation repair protein were discussed.105 A dinuclear dithiolene complex containing two- and three-co-ordinate mercury centres with three di§erent ligand co-ordination modes has been crystallographically characterised.106 Reactions of [Hg(2-Phpy)(OAc)] and [Hg(2-Phpy)(S 2 PPh)] with Ph 2 P(S)SH led to the isolation of [Hg 2 (S 2 PPh 2 ) 4 ] which was found by X-ray analysis to form centrosymmetric dimers based on eight-membered rings.107 X-Ray crystallography has revealed tetrahedral geometry for mercury in [HgX 2 L 2 ] (X\Cl, Br or I; L\dimethylthioformamide); molecules are held in layers by weak intermolecular CH· · ·X bonding. Vibrational spectra and calorimetric measurements were also presented.108 The syntheses of [HgRMS(O)PPh 2N] (R\Me or Ph) have been reported; for R\Me a dimeric structure based on (HgSPO) 2 rings was observed and these were linked to form chains via Hg· · ·O secondary contacts.109 The structure of [Hg(Me)(SC 6 H 4 NO 2 -2)] revealed a linear S–Hg–C arrangement with additional secondary contacts to oxygen (intramolecular) and sulfur (intermolecular) making the geometry trigonal bipyramidal.110 The syntheses and structures of linear [HgSe 2 ]2~ and tetrahedral [Hg(Se 4 ) 2 ]2~ have been reported.111 Halogen-donor ligands Tetrahedral, T-shaped and linear mercury centres were observed in [Ru(NH 3 ) 6 ] [HgCl 4 ][HgCl 3 ]·HgCl 2 ·H 2 O.50 The structures of [HL] 2 [HgCl 4 ] (L\4-benzylpiperidine) and [H 2 pip] 2 [HgCl 4 ] both showed distorted tetrahedra linked by NH· · · Cl bonding.112 The structure of [C(NH 2 ) 3 ][Hg 2 Cl 5 ] contained distorted octahedra around mercury with two HgCl 2 units linked by a chloride ion and intercon- 144 I.B.Gorrellnected through a common square-planar chlorine to form layers.113 Reaction of NiL (L\5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine) and HgBr 2 a§orded [NiLHgBr] 2 [Hg 2 Br 6 ], the crystal structure of which revealed a [Hg 2 Br 2 ]2` group linked to the NiL units via Hg–C bonds to the central carbon of the diiminate.114 The synthesis and structures of the semiconductors [M 6 Br 12 (H 2 O) 6 ][HgBr 4 ]·12H 2 O (M\Nb or Ta) have been reported.115 Two phases of [bets] 4 [Hg 3 I 8 ] have been synthesised and X-ray analysis of one showed [Hg 2 I 6 ]2~ anions linked by HgI 2 molecules.116 The preparations and structures of [Hg(diaza-15-crown-5)I][Hg 2 I 6 ] and [Hg(diaza-18-crown-6)I][Hg 2 I 6 ] have appeared; the former is a salt and the latter contains an iodine bridge between cation and anion.117 Mercury–transition metal complexes The new organometallic tridentate ligands, trans-[Fe(CO) 3 L] [L\2-(diphenylphosphino) pyrimidine] and trans-[Fe(CO) 3MPEt(Ph)pyN2 ] have been used to prepare complexes with HgX 2 (X\Cl, Br, I or SCN) and M(SCN) 2 (M\Zn, Cd or Hg), respectively; both contain Fe–M bonds.118 Reaction of trans-[Fe(CO) 2 (CS 2 )(dppy)] with HgX 2 (X\Cl or SCN) yielded [FeX(CO) 2 (k-dppy) 2 HgX] with a FeI–HgI bond.119 A structural and bonding study of [HgMFe[Si(OMe) 3 ](CO) 3 (k-dppm)N2 Cu]` has been reported.120 A spectrophotometric and electrochemical study of the competitive reaction between mercury(II) and trans-[Cr(NH 3 ) 4 (NCS)(CN)]` has appeared.121 The synthesis and characterization of the linear trimetallic species Hg[g5-BzC 5 (CO) 3 M] 2 and Hg[g5-HO 2 CC 5 H 4 (CO) 3 M] 2 (M\Cr, Mo or W) have been described.122 The crystal structures of [HgPBu5 2 (k-PPh 2 )M(CO) 5 ] (M\Cr, Mo or W) revealed dimers based on Hg 2 P 2 rings.123 The crystal structures of the anions [Re 7 C(CO) 21 (k3 -HgX)]2~ (X\OH or SC 6 H 4 Br) have appeared.124 The compounds Hg[R 2 NbL] 2 (R\g5-C 5 H 4 SiMe 3 ; L\CO,PMe 3 or Bu5NC) have been prepared and act as sources of niobium(II) species via cleavage of the Hg–Nb bond.125 The syntheses and molecular structures of [MOs 3 (CO) 10 (k-X)N2 (k-Hg)] (X\Cl or I), [MOs 3 (CO) 10 (k-Cl)N2Mk-HgOs(CO) 4N2 ] and cis-[Os(CO) 4M(k-Hg)Os 3 (CO) 10 (k-Cl)N2 ] have been reported.126 The preparations, bonding and crystal structures of the bicapped trigonal prismatic 86-electron clusters [Pt 6 (k3 -HgX) 2 (k-CO) 6 (k-dppm) 2 ] (X\Cl, Br or I) have been described127 as have the syntheses and crystal structures of [PtMCH 2 C 6 H 4 P(o-tol) 2 -iC,PN(S 2 CNMe 2 )HgI(k- I)] 2 and [PdBr(S 2 COEt)Mk-P(o-tol) 2 C 6 H 4 CH 2 HgBr]·0.5HgBr 2 ·C 2 H 4 Cl 2 .128 References 1 M.Westerhausen, M. 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ISSN:0260-1818    

DOI:10.1039/ic094137

出版商:RSC    

年代:1998

数据来源: RSC